Current and historic US Highways
serving the Ucolo area

This stretch of highway has seen an inordinate amount of numbering changes. The original US route crossing the stateline here was US 450, which ran between Walsenburg CO and Crescent Jct UT. In 1934, US 450 in Colorado was replaced by an extended US 160, but Utah kept the 450 designation in their state for a few more years. The scan below shows a 1934 map which captured that brief moment in time:

That was brought to my attention by Steve Lockwood. In 1939, US 160 replaced the remainder of US 450 through Utah. In 1970 the US 160 designation was rerouted to go southwest out of Cortez CO (instead of northwest), so this route was renumbered as an extension of US 666. That remained the case until 2003, when all of US 666 was replaced with US 491. The stateline photos below are from July 2004; this first one is looking into Colorado:

From about 1934-1939, that was the east end of US 450 and the west beginning of US 160. Note the "South" tab - the photo below shows the sign directly across the road, heading the opposite direction:

Utah signs US 491 "East/West", which is appropriate in that state. This was once the west end of US 160, and the east beginning of US 450.