History of Colorado's boundaries

• What was "Colorado" before it became one of the United States?  

• What is the legal definition of "Colorado"?

• How and when was that definition physically established on the land?

My primary source for this page was the excellent book Colorado Mapology by Erl H. Ellis (a full list of sources can be found at the bottom of this page).  There is no substitute for that book, and I am certainly not attempting to recreate Ellis' work on a webpage.  Rather, this was my approach: starting in the 1990s, I created some webpages with photos and information about each of the corner points along Colorado's border (the pages for each of those points are linked as appropriate within the text of this page).  I became increasingly curious about the history of those points and the surveys that established them, which is what led me to Colorado Mapology.  I particularly appreciated this quote from Ellis' introductory paragraphs:

I reached a point where I needed to compile all of my research into a catch-all page that would provide the historical context behind all of Colorado's boundary points.  Personally, I found it helpful to arrange all of the information chronologically (which is different than the way Ellis presented his information).  So this page is simply the result of all that.  If you find it interesting, let me again recommend the aforementioned book.

Future Colorado as a part of other nations

1521: Upon their conquest of the Aztec Empire, Spain was the first European nation to lay claim to a vast region of the North American continent, including all of the area that would one day become Colorado.  Spain was nominally in control for the next three centuries, although of course that does not account for the Native Americans who occupied this land (and had done so since prehistoric times).

1785: The U.S. adopted a method by which its massive holdings of public land would be surveyed and subdivided in order to facilitate settlement.  This came to be known as the Public Land Survey System, and it incorporated such concepts as Principal Meridians, Base Lines, Townships, Ranges, Sections, and so forth.  Excepting 18 colonial states (and Texas and Hawaii), the remaining 30 western and midwestern states would eventually be surveyed under this system.  However, there were some notable exceptions, i.e. areas in western states that were not surveyed under the PLSS.  These included some National Parks, various types of reservations, and land grants that would be approved when the area was still under the control of the Mexican government.  Seven of these grants included land in future Colorado, the first of these being approved in 1832 (see below).

1800: France regained control of "Louisiana" from Spain.  The following map shows the situation just prior to the United States' acquisition of Louisiana:

1803: The US purchased from France the area known as "Louisiana", extending its holdings westward to the edge of Spanish territory.  Since the Great Divide formed the border between the U.S. and Spain, an international boundary (along line b-i) ran through future Colorado:

In 1804 this area was designated as the Louisiana District; in 1805 it was organized as Louisiana Territory.  Then in 1812, in order to avoid confusion with the new US state of Louisiana (which was carved out of Louisiana Territory), the remainder of the area was redesignated as Missouri Territory.

1819: The Adams-Onis Treaty defined the boundary between the US and Spain.  Whereas Spain formerly controlled only the western slope of future Colorado, she now additionally controlled the southern part of future Colorado (all land south of the Arkansas River):

1821: Mexico declared independence from Spain, so after that time it was Mexico which had possession of those parts of the future Colorado.  Also, Missouri became a State, with the remainder of former Missouri Territory (nee Louisiana Territory, including roughly the northeastern quadrant of future Colorado) reverting to unorganized public domain.  Now a different international boundary ran through future Colorado.  Starting in the east, it ran along the Arkansas River to its source, then on a line due north from there:

1832: Continuing a practice which had been used when Spain controlled the area, Mexico approved a land grant known as the Tierra Amarilla.  This was primarily in future New Mexico except for a relatively small tip that extended northward into future Colorado (the "knob" in the southeast corner of today's Archuleta County is coincident with the boundary of the Tierra Amarilla grant).

1833: Mexico approved the Conejos Grant.  In Colorado, this covered much of modern-day Conejos and Rio Grande counties, and it also extended into New Mexico.  But the early attempted settlements within this grant failed due to ongoing conflicts with natives.

1836: Texas declared itself independent from Mexico.  Included in its claim was some of what would later become parts of southern and western Colorado.  However, Mexico never acknowledged this claim, and Texas never had defacto control over these northwestern areas of its claim.  As evidence of that, see the next item.

1843: Mexico approved four additional land grants which included areas within the future boundary of Colorado.  Each of these land grants were entirely within the area that Texas had claimed in 1836:

• The Beaubien and Miranda Grant, which is now better known as the Maxwell Grant.  Like the Tierra Amarilla, most of the Maxwell lies in modern New Mexico, but a rather sizable strip extends into Colorado, occupying the southwestern corner of Las Animas County.

• The Gervacio Nolan Grant, which was generally south and west of Pueblo along the St. Charles River.

• The Sangre de Cristo Grant, which in Colorado is essentially coextensive with modern Costilla County (although the grant also extends southward into New Mexico).

• The Vigil and St. Vrain Grant (also known as the Las Animas Grant).  Of all the Mexican land grants in future Colorado, this one contained the most acreage, including the entire area between the Arkansas and Purgatoire rivers, all the way west to the crest of the Sangre de Cristo Mountains.

• Here is an artistic and informative map (from History Colorado) which illustrates all of the Mexican land grants in the state.  Taken together, they comprised a substantial area in the south central part of Colorado.

1845: The United States annexed Texas and therefore gained possession of the parts of future Colorado which had formerly been claimed by Texas.  But Mexico still disagreed, and as a result the two countries were soon at war over the issue:

1848: The Mexican-American War ended with the signing of the Treaty of Guadalupe Hidalgo.  Mexico ceded possession of a vast area, including what would later become western and southern Colorado:

This marked the first time that the entirety of future Colorado was brought within the fold of US territory.  It is also important to note that, as part of the terms of the treaty, the U.S. agreed to recognize the property rights of people who had recently been granted land when the area was still a part of Mexico.  However (as we will see below) that promise was not upheld in every case.

Future Colorado as a part of various U.S. Territories

1850: The US adopted the Washington Meridian as its prime meridian.  This meridian was the reference point for many of the state boundaries that Congress would define during the next few decades, including Colorado's.

1850: Utah Territory was created on Sep. 9.  Thus all of future Colorado that lay west of the Great Divide was a part of Utah Territory:

The Congressional act defined the south boundary of Utah Territory as the 37th parallel.  Line h-i on the map above is shown in black, because this marked the first time that a future boundary of Colorado was defined on paper.  Specifically, the south boundary of Utah Territory from Point h (future Four Corners) to Point i (the Great Divide) would eventually form part of Colorado's south line.  However, this line was not yet surveyed.

1850: New Mexico Territory was created on Dec. 13.  This encompassed some land that would later become part of southern Colorado, specifically land between the 37th and 38th parallels, east of the Great Divide, and west of the 103rd Meridian:

1854: William Pelham was appointed Surveyor General of New Mexico Territory.  He wanted the N.M. Principal Meridian to run close to Santa Fe, and he wanted the Base Line to be located near the confluence of the Rio Puerco and the Rio Grande.  The location he ended up choosing for the Initial Point was the top of a small butte rising about 200' above the west bank of the Rio Grande, about ten miles downstream from the aforementioned river junction, and about two miles down from the mouth of the Rio Salado (today this location is near the community of San Acacia, off I-25 between Belen and Socorro.)  A monument at this Initial Point was constructed in 1855, and surveys began shortly afterward (see 1858).  Ultimately, roughly the southwestern quarter of Colorado would be surveyed using the New Mexico Meridian as the reference point.

1854: Kansas and Nebraska territories were created.  Thus all of future Colorado east of the Great Divide and north of the 40th parallel became part of Nebraska Territory, and all of future Colorado east of the Great Divide and between the 37th and 40th parallels became part of Kansas Territory (except for that land which was already part of N.M. Territory, as described above).  

It was determined that the 40th parallel would serve as the Base Line for surveys in both territories (Kansas and Nebraska).  It was also determined that the point where this Base Line intersected the Missouri River would be considered the meridian line between Ranges 28 and 29 East.  In other words, the yet-to-be-established Sixth Principal Meridian would be located 108 miles west of the Missouri.  Today this Initial Point is located one mile northwest of the town of Mahaska KS (at the quadripoint of the Nebraska counties of Thayer and Jefferson, and the Kansas counties of Republic and Washington).  Ultimately over three-quarters of future Colorado would be surveyed using the Sixth Principal Meridian as the reference point.

1857: the south line of Kansas Territory was surveyed along the 37th parallel, with the intention of ending at Point g (where the line met N.M. Territory, legally defined as the 103rd meridian west).  This line ran through future Corner f, although that point was not established at the time (there being no reason to, since no boundary had yet been defined there).  Three separate parties were sent out for this survey.  J.E. Wyess and his party did the surveying and placement of the monuments.  Hugh Campbell's party established astronomical stations and helped to keep the Wyess party on the 37th parallel.  Lt. Col. Joseph E. Johnston was the official head of the expedition, and his cavalry unit was ostensibly there to protect the other parties, although evidence suggests his real purpose was to study the country being traversed for the purpose of railroad construction.  The monument placed by this expedition at theoretical Point G came to be known as the Johnston Monument.  Modern topographical maps show that the Johnston monument was almost exactly on the 37th Parallel, but due to an error on the part of the astronomers, it was nearly 4.5 miles west of the 103rd Meridian (see 1859).  And, further to the east, this line veered about a half-mile south of the 37th Parallel (see 1872).  So Point G was the location of the first attempted monument on the border of future Colorado, but interestingly, the correct location of Point G was also the last of Colorado's corner points to be legally settled (43 years later; see 1900).

1858: The first surveying activity which took place in future Colorado was done in the San Luis Valley.  Pelham (see 1854) hired Alexander Wilbar as Deputy Surveyor for the job.  48 miles east of the New Mexico Principal Meridian, Wilbar established the First Guide Meridian East, and then he ran that line north into an area which is now part of Conejos County.  In other words, this land was inside the Conejos Grant, so it probably should not have been included in the survey, but at the time this land grant was only sparsely settled.

1859: Officials in DC determined that the Johnston Monument (at Point g) was in the wrong location, so they supplied the correct calculation to Capt. John N. Macomb, who established a new monument at what he determined to be the correct location.  Modern topos show that this monument was almost exactly on the 37th parallel.  However, it was later found that the Macomb Monument was also incorrectly located, this time about 2.5 miles west of the 103rd Meridian (see 1868 and 1881).

1859: The second official survey to take place in future Colorado was based on the Sixth Principal Meridian.  Ward Burnett (Surveyor General) hired Jarret Todd and James Withrow as Deputy Surveyors, and their task was to run the Base Line west along the 40th parallel all the way to the "summit of the Rocky Mountains" (i.e. the Great Divide, which formed the western boundary of Kansas and Nebraska territories, separating them from Utah Territory).  This line ran through Point e, although that point was not established at the time, since no boundary had yet been defined there.

1860-61: The U.S. Congress issued rulings regarding several of the earlier Spanish and Mexican land grants.  Many were confirmed, including some which covered land in future Colorado: the Tierra Amarilla, the Maxwell, and the Sangre de Cristo.  To this day, those land grants have never been surveyed under the PLSS.  The Nolan Grant, as well as the Vigil and St. Vrain Grant, were also approved during this time, but eventually most of the land originally included in both of those grants was repossessed by the U.S. government as public domain, surveyed under the PLSS, and opened for settlement.  Nevertheless, the USGS 1:100 scale topo maps titled "Pueblo" and "Walsenburg" (published in the 1980s) still showed a few areas which were labeled "Nolan" and "Vigil and St. Vrain" and which lacked PLSS section lines.  The Conejos Grant was eventually rejected outright by the U.S. Court of Private Land Claims.  The original Baca Grant (near Las Vegas NM) was invalidated, but as compensation to the Baca family heirs, they were granted five parcels elsewhere, including one in Colorado (see 1864).

1861 (Jan. 29): The State of Kansas was created, with its western border defined as 25 degrees west of Washington.  The portion of former Kansas Territory that was excluded from the State of Kansas (i.e. west of 25 degrees) would very soon become part of Colorado Territory, but for the next 30 days, this land was not a part of any Territory and thus would have reverted back to unorganized public domain.  The map below indicates that line e-f had been legally defined but not yet surveyed.  It also shows line f-G in black (because it had been surveyed), but dotted (because this was not the final boundary line).  Point G is shown with a capital letter (because both Johnston's and Macomb's locations had been monumented), but in italics because ultimately neither of those monuments would be accepted as the correct location for Point G:

Colorado as a U.S. Territory

1861 (Feb. 28): the Territory of Colorado was created, with the north and south boundaries defined as the 37th and 41st parallels, and the east and west limits described as 25 and 32 degrees west of the Washington Meridian.  Colorado Territory encompassed areas that had previously been part of Kansas, Nebraska, New Mexico, and Utah territories.  The new Colorado Territory had common borders with the State of Kansas (line e-f); the Public Land Strip (future Oklahoma panhandle, line f-G); New Mexico Territory (line G-h); Utah Territory (line b-a-h); and Nebraska Territory (line b-d-e)...

...however, that arrangement lasted for only a couple days.  Nebraska Territory was extended west, absorbing land that had been part of Utah and Washington territories.  So then Colorado Territory's border with Utah Territory was only along line a-h, whereas the border with Nebraska Territory was now along line a-b-d-e:

1863: New Mexico Territory was divided into two roughly equal areas, with the western half being designated Arizona Territory.  Four territories (Arizona, Colorado, New Mexico, and Utah) all had a corner at point h (which at that time had still not been surveyed):

1863: Shortly after the above change, the western part of Nebraska Territory was redesignated as Idaho Territory.  The boundary was defined as 27 degrees west from the Washington Meridian, so Point c on Colorado's border was now defined on paper.  Colorado Territory now shared a border with a new territory (Idaho, along line a-b-c), whereas its border with Nebraska Territory was reduced to line c-d-e:

1864: Colorado Territory's boundary with Idaho Territory (line a-b-c) lasted only about one year before becoming a boundary with Dakota Territory:

1864: Baca land grant #4 was entirely in Colorado.  It was part of the compensation awarded to the Baca family in exchange for their original grant near Las Vegas NM, which had been occupied by other settlers and ranchers (see 1860-'61).

1867 (Mar. 1): The State of Nebraska was created.  So now, in addition to Kansas, Colorado Territory shared a border with a second state:

1868: Ehud N. Darling was tasked with surveying the north boundary of New Mexico Territory along the 37th parallel.  At the time the Macomb Monument (see 1859) was still considered the correct location for the northeast corner of New Mexico (Point G), so that was to be Darling's initial point, and he was to work westward from there to Corner h.  However, it was later discovered that Darling misidentified a different monument on the Johnston line as the Macomb Monument (see 1874).  More consequentially, in the vicinity of the town of Edith (near Pagosa Springs), Darling did not do any surveying between the Navajo River and Abeyta Canyon (nee Ewell Canyon) due to rough terrain.  On opposite sides of this gap, his boundary line was misaligned by nearly a half-mile (see 1901 and 1917).  His survey ended at theoretical Corner H (Four Corners), although it appears his terminal point was at what he believed to be 109 degrees west of Greenwich (rather than at the meridian defined by law, which was 32 degrees west of Washington).

Also in 1868: Colorado Territory's boundary with Dakota Territory (line a-b-c) became a boundary with the new Wyoming Territory:

1869: Line C-D was surveyed by Oliver N. Chaffee.  Sometime after May 29, he started at an astronomical station in Julesburg, measured the distance north to the 41st parallel, then turned east until reaching the South Platte (west of Corner D).  Then he returned to the Julesburg initial point and ran west, establishing Corner C on Aug. 17.  Then he returned to the South Platte and ran east, establishing Corner D on Sep. 24.

1869: Line D-E surveyed by Chaffee, who after establishing Corner D (above) ran south. He expected to find markers along the 40th parallel (see 1859), but did not, so using his own calculations he established Corner E on about Oct. 1:

1872: John J. Major surveyed line E-F, intending to start at Corner E.  He found the monument set by Chaffee three years earlier (see 1869), but already by then it had been leveled and buried, so Major reset it.  From there Major ran south, reaching the Johnston line and setting a monument for Corner F (presumably he was aware this was about a half-mile south of the true 37th Parallel; see 1857).

1873: Edwin Burwell successfully located monuments along the 40th parallel (see 1859), allowing him to determine that Chaffee's monument for Corner E was over 600 feet south of the true location.  Burwell established a new monument at the correct position for Corner E (Chaffee's monument still exists to the south).

1873: Line A-C surveyed by A.V. Richards.  He ran the south boundary of Wyoming Territory, starting at Corner C on June 5.  His party surveyed through Corner A sometime after Aug. 20, but he did not establish the location of that corner at the time (see 1879).  (Richards actually continued west of Corner A to the southwest corner of Wyoming, which is 34 deg. west of Washington).

1874: John J. Major was tasked with surveying the 53-mile line F-G.  He started at Corner F and worked west.  Near his 42nd mile, he found the marker at Darling's 1868 starting point, which was intended to be at the 103rd Meridian, but it was actually about 12 miles east of the true meridian.  Major reasoned this was probably because Darling had found a marker on the Johnston line (see 1857) and erroneously believed it to be the Macomb Monument (see 1859).  In order to accommodate this discrepancy, at roughly his 36th mile, Major angled his line gently northward, reaching the Johnston/Darling line at mile 42.5.  From there he continued along the Darling line through the Macomb Monument to the Johnston Monument.

1875: Chandler Robbins established a more accurate location of Corner H (Four Corners) at a point roughly a mile east of Darling's location (see 1868) and erected a substantial stone monument there.  This was the initial point for a survey running south along the boundary between Arizona and New Mexico territories.

Colorado as a State

1876 (Aug. 1): the State of Colorado was created, defined by the same boundaries that had been specified for the Territory back in 1861:

1878: Rollin J. Reeves began at the Robbins/Four Corners Monument (Corner H) on Sep. 11 and surveyed to the north, establishing the boundary between Colorado and Utah Territory.  Work stopped on Nov. 10 at the 150 mile mark.

1879: Reeves completed his survey north to Corner A on July 19.  At that time, Colorado's north, east, and west borders had been established by surveys that still govern the boundaries today.  Still in dispute were Point G and the Colorado-New Mexico border:

1890: The "Public Land Strip" (future Oklahoma's panhandle) became a part of Oklahoma Territory, which shared a border with Colorado along line F-G:

1890 (Jul. 10): The State of Wyoming was created, sharing a boundary with Colorado along line A-C:

1896 (Jan. 4): The State of Utah was created, sharing a border with Colorado along line A-H:

1899: Hubert D. Page and James M. Lentz located the Robbins/Four Corners Monument at Corner H, but found it had been disturbed and damaged, so they reset it.

1900: Levi S. Preston was tasked with re-surveying the north boundary of New Mexico between the Macomb Monument and the Cimarron Meridian (i.e. the 103rd Meridian).  As a part of that survey he established the fourth (and final) location of Corner G.  Modern topos show that the Preston monument is about .17 mile due south of the Chaney-Smith Monument (see 1881).  It is almost exactly on the 37th parallel, and a small fraction of a mile west of the 103rd Meridian (see 1928).

1901: Howard B. Carpenter surveyed the boundary between Utah and Arizona Territory, terminating his work at Corner H, and finding that the remonumentation by Page and Lentz was still in good condition.

1901: Colorado wanted to re-survey its south boundary, so Governor Orman appointed Charles A. Johnson to oversee that project, who in turn commissioned Blair Burwell to do the survey.  He discovered one error near the Little Chama River, where corner 202 was 726 feet south of corner 196.  He also discovered Darling's gap with a significant offset (see 1868; discussed in greater detail under 1917).  However, before this survey was completed, it was known that a Federal survey was to take place, so work on this State survey was stopped.

1902: Congress made an appropriation for the re-establishment of the 37th parallel between the 102nd and 109th meridians.  The General Land Office commissioned Carpenter to perform this re-survey.  Rather than retracing the previously-established lines, he was instructed to start from scratch and to obliterate all of the Darling corners and monuments.  He was instructed to start at the 109th meridian, although actually he most likely started at Four Corners, where he had just been (see 1901).

1903: Carpenter completed his task.  His initial point was some distance north of the Darling line, and to the east of there most of the Carpenter line remained north of the Darling line, although it intersected and crossed to the south near the Macomb Monument.  For a brief time the General Land Office recognized the Carpenter line as the boundary between Colorado and New Mexico.

1907 (Nov. 16): The State of Oklahoma was created.  Colorado now had a common border with Oklahoma along line F-G:

1908: Congress passed a joint resolution stating that the Carpenter line formed the true boundary between Colorado and New Mexico/Oklahoma.  However, the President vetoed this resolution, and Congress took no further action.  So the General Land Office abandoned its recognition of the Carpenter line and reverted back to the Darling and Major/Preston lines as the correct boundary.

1908: Arthur D. Kidder started a survey at the southeast corner of Baca County.  About 11 chains east of there he did not find the expected marker for Darling's 2nd mile corner west of the Macomb Monument (nor was he able to find Darling's 1st mile corner).  But between those two, he did find the 1857 Johnston Monument.  It was only about 19 feet north of the Darling line (which is remarkably accurate).  However, it was nearly two miles west from the Macomb Monument, which itself was more than two miles west of the true 103rd Meridian.  At the time, Kidder described the Macomb Monument as a pile of stones (see 1928).  He noted that the existing monument at Corner F was "very satisfactory", but he replaced it with an iron post and brass cap.  After that, Kidder reestablished the southern part of line E-F, heading north about 27 miles (to the Sixth Correction Line South).

1912: The US legally rejected the Washington Meridian and agreed to recognize the Greenwich Meridian as its prime meridian (although this arrangement had already been in practice for the past three decades; see 1883).

1912 (Jan. 6): The State of New Mexico was created.  Colorado now had a common border with New Mexico along line G-H (although that line was still not finalized; see 1919):

1912 (Feb. 14): The State of Arizona was created.  The southwest corner of Colorado now met the northeast corner of Arizona at Four Corners (Point H):

1915: As part of a survey, Clayton R. Burt found the Four Corners monument reconstructed by Page/Lentz.

1917: William C. Perkins carried out a partial re-survey authorized by the General Land Office.  He noted the significant offset in the Darling lines near Edith (see 1868 and 1901) and formally established the jog between the two by placing two angle points in what he referred to as Ewell Canyon, but which is labeled on more recent maps as Abeyta Canyon.  This offset lies along the south boundary of Archuleta County, and is quite conspicuous on larger-scale maps.  This image shows the USGS 1:24k scale topo map coverage of that area:

1919: New Mexico filed an action against Colorado with the U.S. Supreme Court.  Despite being aware of the fact that previously-accepted boundaries are the defacto boundaries, NM thought it may have a chance to demonstrate that the Darling line constituted a gross irregularity and thus could not be considered a valid boundary line.

1925: The Supreme Court handed down its decision, finding in favor of Colorado, meaning:

• The lawful boundary between Colorado and New Mexico was the Major line of 1874 east of the Macomb Monument, and the Darling line of 1868 to the west (incorporating the Perkins angle points of 1917).

• Since Carpenter had been instructed to destroy all evidence of the Darling line, Kidder (see 1908) was appointed to perform another survey to re-establish the entire boundary.  

Neither state was particularly thrilled about having to provide funding for yet another survey, and their failure to do so timely led to a lengthy delay.  But, at long last, the border between Colorado and New Mexico was considered final:

1928: As Kidder began his survey work, he again found the Macomb Monument (see 1908) and this time he reconstructed it.  He also found the Cheney-Smith Monument (see 1881) and the Preston Monument (see 1900) which he rebuilt, and that version is the one that still exists today at Corner G.

1931: Kidder performed additional field work, with more in 1932, at which point 236 miles were completed, leaving another 94 miles yet to be surveyed.  During this period Kidder found all of the Perkins' monuments (see 1917).

1931: Everett H. Kimmell located the Page/Lentz remonumentation at Four Corners (see 1899), but noted that it had been disturbed and damaged, so he constructed the current concrete monument there.

1962: A paved highway was completed through the extreme southwest corner of Colorado, providing easy access to Point H.  This allowed the Four Corners to become a tourist destination, and as a result the monument has been improved and/or reset multiple times (1962, 1992, and 2010).