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100 years of US routes: 1926-2026
Unlike most 3-digit US routes, the following do not branch off from the 2-digit routes that are implied by their numbers:
US 101
US 163
US 400
US 412
US 425
These routes have numbers that significantly deviate from the US route numbering methodology. These highways have never come anywhere close to their implied "parent", nor to any of their implied "siblings". At the time they were commissioned, other numbers were available which would have conformed to the numbering guidelines.
US 101: This was among the original 1926 routes, and not everyone considers its number to be a violation. Granted, there is a certain symmetry with US 1 running along the East Coast, and US 101 on the West Coast. But when viewed in the context of all other US routes, the number implies a branch of US 1. The route could have been assigned US 99 or US x99.
US 163: When this route was commissioned in the early 1970s, there was no number that would have worked perfectly. Looking at a modern map of the area, one might think US x91 would have been a good choice. However, US 191 had not yet been extended through eastern Utah. So US 163 went all the way up to Crescent Jct, and connected only with even-numbered routes: US 160 at its south end, US 666 in the middle, and US 6-50 on the north. Given that, US x60 would have been a better choice (even though it was a north/south route) or US x89 (even though it did not connect with US 89). Neither of those would have been ideal, but US 163...? It has been reported that Arizona and Utah originally suggested US 164, but since it was a north/south route, AASHTO responded that it needed to be an odd number, so they subtracted one to come up with 163. (More on this page).
The "4xx series" routes below were commissioned in the 1980s and 1990s. At least two of them are along "high-priority corridors" and/or a possible future interstate route. But that is not enough reason to justify the fact that they were assigned numbers that are drastically out of sync with the rest of the system.
US 400: Any of these options would have made more sense...
x50 (its westernmost 131 miles are overlapped with US 50)
x54 (it is dual-signed with US 54 for 144 miles through KS)
x66 (it connects with US 166, and it runs along the formerly-proposed I-66 corridor)
...but US 400 never should have been granted US route status at all (read more here).
US 412: It could have been an x70. At the time of its creation, US 70 in TN was the only other east-west route it intersected. But soon afterward US 412 was extended, such that it now also junctions US 270 in OK. And it also intersects several other east-west US routes:
x56 (its westernmost 135 miles are overlapped with US 56)
x60 (it is dual-signed briefly with US 60 in OK)
x62 (it is concurrent with US 62 through much of AR)
x64 (it is co-signed with US 64 through much of OK)
US 425: Originally this route connected to US 65 on one end, and US 165 on the other, so US 265 would have been a perfect number. Now that US 425 has been extended south to Natchez, the entire thing should be renumbered as US 65 [map]. The current segment of US 65 between Pine Bluff AR and Clayton LA could be renumbered US 265... and then the number "425" would be nothing but an infamous historical footnote.
The routes below have numbers that are/were "technical violations": although these routes never actually connected with their implied "parent", they were close enough that one could argue their numbers were acceptable nonetheless.
US 104: Maybe x20 would have been a better choice. But, in its defense, it was on roughly the same latitude as US 4 [map].
US 121[ii]: While it does connect with the historic US 21 corridor [map], this route was created some 30 years after US 21 had been decommissioned in that area. US x19 would have made the most sense, and US x23 would have worked better, too.
US 164[ii]: Today US 64 does connect with the former route of US 164 (at Teec Nos Pos AZ). But during the brief period when 164 existed, the west end of US 64 was in Santa Fe NM [map]. US 164 connected with US 66 and US 89 on one end, and US 666 and US 160 on the other... so US x66 probably would have been a better choice. (US 766? Or else US 366 [iii] and US 566 were available.) On the other hand, much of the route lay along what had only recently been designated as AZ hwy. 64, so the number "164" was probably intended to minimize confusion (more here).
US 410: It could have been x95, x97, or x99... but it was an east-west route. Playing off US 730, it could have been US 930 (the only remaining x30 number then available), but that seems like a stretch. So US 410 was a pretty good choice, all things considered [map].
US 830: Ran parallel to (and right across the Columbia River from) its implied parent, US 30 [map].
A handful of US routes connect(ed) with a sibling, but never their implied parent. In other words, they are/were "branches of branches". So these are not really numbering violations -- only idiosyncrasies.
US 701: Connects with US 301 and US 501 [map].
US 309: Connected with US 209 [map].
US 411[ii]: Connected with US 311 [map].
US 217: Connected with US 17-1 [map].
US 220: Connected with US 120 [map].
US 566: Connected with US 366[I] [map].
US 187: Connected with US 287 [map].
US 491: Connects with US 191 [map].
US 295: Connected with US 195 [map].
US 395: Connects with US 195 [map].
Several existing US routes no longer connect with their implied parent, but did historically. So these were not numbering violations at the time of their commissioning. And now a few of them are interesting historical relics, because their implied parent routes no longer exist.
US 310: Connected to US 10 at Laurel MT [map].
US 311: Connected to US 11 at Roanoke VA [map].
US 411: Connected to US 11 at Greeneville TN [map].
US 212: Connected to US 12 at Willmar MN and Miles City MT [map].
US 219: Connected to US 19 at Princeton WV [map].
US 138: Connected to the no-longer-extant US 38 at Sterling CO [map].
US 641: Connected to US 41 at Evansville IN [map].
US 158: Connected to US 58 at Franklin VA [map].
US 166: Connected to the no-longer-extant US 66 at Baxter Springs KS (and later also at Joplin and Springfield MO) [map].
US 266: Connected to the no-longer-extant US 66 at Oklahoma City OK [map].
US 276: Connected to US 76 at Laurens SC [map].
US 277: Connected to US 77 at Oklahoma City OK [map].
US 180: Connected to US 80 at Weatherford TX [map].
US 380: Connected to US 80 at Cisco TX [map].
US 181: Connected to US 81 at San Antonio TX [map].
US 281: Connected to US 81 at San Antonio TX [map].
US 183: Connected to US 83 at Vivian SD, Dresden KS, and Junction TX [map].
US 283: Connected to US 83 at Norton KS and Junction TX [map].
US 191: Connected to US 91 at Idaho Falls ID and Brigham City UT [map].
US 199: Connected to the no-longer-extant US 99 at Grants Pass OR [map].
Research and/or image credits: Dale Sanderson
Page originally created 1998;last updated Sep. 6, 2025.
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