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100 years of US routes: 1926-2026
(referred to as Corner E on this page)
According to the Congressional definition of the boundary of Colorado, this point is theoretically where the 40th parallel north latitude intersects 25 degrees west longitude as measured from the Washington Meridian*. However, the first efforts to survey these boundaries and monument this location occurred between 1869 and 1873 -- and due to the technological limitations of that day, it is not exactly right (although those surveys do define the official boundary, regardless of accuracy).
*Many American surveys between 1850-1884 were based on the Washington Meridian, which was officially abolished by Congress in favor of the Greenwich Prime Meridian in 1912. "25 degrees west of Washington" is a few miles away from the 102nd degree of longitude west of Greenwich.
1859 was the year of the first survey to run through this point, when Jarret Todd and James Withrow were tasked with surveying the boundary between Kansas and Nebraska territories, which was along the 40th parallel. However, they did not monument this location, as no boundary point had yet been defined there.
In 1869, after establishing the northeast corner of Colorado, Oliver Chaffee turned south for 69 miles and looked for indications of the survey along the 40th parallel from ten years earlier. Not finding any, he made his own determination of where the monument should be located and established one there.
In 1873, Edwin Burrell successfully located the 1859 survey of the 40th parallel, which allowed him to determine that Chaffee's monument from four years earlier was about 600 feet too far south, so he established a monument at the correct location...
...but interestingly at the time of his 1969 visit, Erl Ellis photographed only the Chaffee Monument, but not the actual tri-state corner. By the time of Ellis' 1983 book Colorado Mapology, he was clearly aware that Chaffee's monument was not in the correct location, but not much detail was provided about Burrell's monument at the true tri-state corner.
This first photo was looking southeast; visible in the foreground is the Chaffee's limestone marker. Following that are two closeups that show what was left of the inscriptions "25° W" and "40° N":
Ellis, 1969
Ellis, 1969 (looking north)
Ellis, 1969 (looking west)
That marker still exists, but since then some attention has been given to the true tri-state corner. In 1990 the corner was enclosed with a fence and spruced up to the degree shown in the following photos. At the time of my 1993 visit this corner was a little hard to find; the roads were not all that great. This sign was helpful, though:
Sanderson, fall 1993
The view in this next photo was mostly south, and a little east (roughly the same as the first 1969 photo above -- note the tree in the background). I was standing in the northwest corner of Kansas. The camera was in Colorado; the line of fence posts running diagonally across the photo are on Colorado's east line. Nebraska is just left (east) of the camera. In the distance the breaks of the Arikaree River are visible (the point where that stream flows out of Colorado is the lowest elevation in the state):
Sanderson, fall 1993
Here is a close-up of the brass cap:
Smith, Feb. 2009
At the tri-state corner was also a mailbox for the visitor register, with a quaint little painting which illustrated each state bird and state flower:
Sanderson, fall 1993
By the time of my 2019 visit, that mailbox was gone, and in its place was this interpretive marker (click for a higher-resolution image):
Sanderson, Aug. 2019
This photo shows the back side of that plaque, and you can also see the dirt track leading southward from the tri-state corner:
Sanderson, Aug. 2019
600 feet in that direction is Chaffee's 1869 marker. I do not have photos, but here is a good one that shows Chaffee's monument in the foreground, and the actual tri-state corner off in the distance.
Research and/or photo credits: Erl Ellis; Dale Sanderson; Scott Smith
Page originally created 1998;last updated Feb. 1, 2026.
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