U.S. Route 40 in Colorado

US 40 in Byers Canyon between Parshall and Hot Sulphur Springs. The Union Pacific railroad line is visible on the left. The Colorado River is at the bottom of the canyon and is not visible.

Entering Colorado to the south of Dinosaur National Monument, US 40 runs east through the small town of Dinosaur along Brontosaurus Boulevard. The route continues a generally easterly course though Moffat and Routt counties, passing through several small communities along the way. It generally follows the course of the Yampa River. US 40 becomes Lincoln Avenue as it runs through historic downtown Steamboat Springs, Colorado.

View along US 40 in Mount Vernon Canyon, Colorado, 1942. Photo by Andreas Feininger.

Taking a circuitous route through Rabbit Ears Pass, Muddy Pass and Berthoud Pass (crossing the Continental Divide each time) it descends the escarpment along the eastern edge of the Rocky Mountains. Just to the east of Empire, it merges with I-70 for the first time. US 40 and I-70 will run concurrently numerous times across the U.S. The route leaves I-70 at exit 244, to the east of Idaho Springs and rejoins it again at between exits 252 and 254 in El Rancho. It parallels I-70, mostly as a frontage road, until the intersection with former State Highway 26 (SH 26) to the south of Golden[2][3]

US 40 westbound concurrent with I-70 BL and US 287 on Colfax Avenue in Denver

Beginning in Golden, US 40 becomes Colfax Avenue, the main east–west thoroughfare through the Denver-Aurora Metropolitan Area. Along with US 40, the entire route along Colfax Avenue is cosigned as Business Loop 70. The route travels northeast through Golden, then turns due east to travel through Lakewood, Denver, and Aurora. Among the sights to be seen along US 40 is Lake Steam Bath, once the location of a thriving health industry centered on tuberculosis sanatoriums. Also along Colfax Avenue in Denver is the Denver branch of the United States Mint, which produces 50 million coins per day. US 40 rejoins I-70 at exit 288, just to the east of Aurora.[3][4][5]

At exit 359 in Limon, US 40 leaves I-70 along Main Street, which it shares with Business Loop 70, US 24, US 287, and SH 71. US 40/US 287 continues to the southeast to the town of Kit Carson. From there, it leaves US 287 and continues east through the towns of Cheyenne Wells and Arapahoe before entering the state of Kansas.[3][4]

State Highway 40 (SH 40) represents the former two-lane alignment of US 40 in Arapahoe and Elbert Counties, prior to its demotion by the then-Colorado Department of Highways when they moved the route to then new I-70 in 1968.

SH 40 begins in Arapahoe County the town of Byers at a junction with SH 36 (N Main Street/Old Highway 36), just across the railroad tracks from downtown. It heads southeast to leave Byers and travel along the flat plains of eastern Colorado for the next several miles. The highway passes through the tiny community of Peoria, where there is an interchange with I-70/US 40/US 287 (exit 322), before passing by the Richmil Ranch Open Space park.

SH 40 then enters the town of Deer Trail, passing along the western edge of town as 1st Avenue as it has an intersection with I-70 BS (Cedar Street). It continues southeastward across the plains to leave Deer Trail and crosses into Elbert County. The highway passes through the tiny community of Lowland, where it has another interchange with I-70/US 40/US 287 (exit 336), before crossing a creek to enter the small town of Agate along 1st Avenue, with SH 40 coming to an end shortly thereafter at a junction with Main Street. Main Street (as unsigned I-70 BS) leads 0.3 miles (0.48 km) west to an interchange with I-70/US 40/US 287 (exit 340).

The entire length of SH 40 is a rural, two-lane, state highway, running parallel to both the eastbound lanes of modern I-70 to its north, as well as a railroad track to its south. SH 40 never goes beyond a half mile from the Interstate.[7]

County	Location	mi	km	Destinations	Notes
Arapahoe	Byers	0.0	0.0	SH 36 (Main Street/Old Highway 36) to I-70 (US 40/US 287) / US 36 – Strasburg	Western terminus; former US 40 follows SH 36 west
	Peoria	6.1	9.8	Peoria Road to I-70 (US 40/US 287)	I-70 exit 322
	Deer Trail	12.3	19.8	I-70 BS (Cedar Street) to I-70 (US 40/US 287)
Elbert	Lowland	20.6	33.2	CR 178 to I-70 (US 40/US 287)	I-70 exit 336
	Agate	24.1	38.8	Main Street to I-70 (US 40/US 287) 1st Avenue	Eastern terminus; former US 40 continues east along 1st Avenue
1.000 mi = 1.609 km; 1.000 km = 0.621 mi

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