U.S. Highway 138 (US 138), commissioned in 1926, is an east–west U.S. Highway in Colorado and Nebraska that travels predominantly northeast to southwest, paralleling the South Platte River and Interstate 76 (I-76). Similarly to the spurs of the former US 66 and US 99, US 138 is an orphan route. US 38 was commissioned in 1926, but US 6 was extended over it to Long Beach, California (it was subsequently truncated to Bishop, California in 1964). Therefore, US 138 still meets its former parent route's path.

U.S. 138 begins in Sterling at U.S. 6 and Business Loop 76. It goes northeast and intersects Colorado State Highway 113 southwest of Iliff. It becomes more easterly as it goes through Iliff, Proctor and Crook, where it intersects Colorado State Highway 55. It continues on to Sedgwick, where it meets Colorado State Highway 59. After passing through Ovid, it then meets U.S. Highway 385 west of Julesburg, and they overlap into Julesburg. Also in Julesburg, U.S. 138 intersects Colorado State Highway 11. U.S. 138 then leaves Julesburg going northeast and enters Nebraska.

Shortly after entering Nebraska, U.S. 138 intersects Interstate 80. It continues east from I-80 and enters Big Springs. At Big Springs, U.S. 138 turns north and ends at U.S. Highway 30.

The western terminus is in Sterling, Colorado, where it met U.S. Route 38 from 1926 to 1931 (US 38 became U.S. Route 6); the eastern terminus is at U.S. Route 30 north of Big Springs, Nebraska. US 138 is an example of a "child" route that has long outlived its "parent"; before U.S. Route 99 was decommissioned in 1964, US 138 was the only US route to not have a "parent" route.

State	County	Location	mi	km	Destinations	Notes
Colorado	Logan	Sterling	0.000	0.000	SH 14 west (Chestnut Street) / US 6 to I-76 – Holyoke, Atwood, Brush, Fort Collins	Western terminus; eastern terminus of SH 14; highway continues as US 6 west (3rd Street south)
					Front Street	Interchange; eastbound entrance only
		​	8.970	14.436	SH 113 north – Peetz, Sidney	Southern terminus of SH 113
		Crook	27.503	44.262	SH 55 south – Fleming	Northern terminus of SH 55
	Sedgwick	Sedgwick	43.413	69.866	SH 59 south – Haxtun, Yuma	Northern terminus of SH 59
		​	54.810	88.208	US 385 north – Chappell, Sidney	West end of US 385 overlap
		Julesburg	56.956	91.662	SH 11 north to I-80	Southern terminus of SH 11
			58.534	94.201	US 385 south to I-76 – Holyoke	Interchange; east end of US 385 overlap
			59.823 0.00	96.276 0.00	Colorado–Nebraska line
Nebraska	Deuel	​	3.06– 3.51	4.92– 5.65	I-80 – Sidney, North Platte	Partial cloverleaf interchange; exit 101 on I-80
		Big Springs	9.44	15.19	L-25B to I-80	Northern terminus of L-25B
		​	11.47	18.46	US 30 – Ogallala, Chappell	Eastern terminus
					Road 207 – Lewellen	Continuation beyond eastern terminus
1.000 mi = 1.609 km; 1.000 km = 0.621 mi       Concurrency terminus       Incomplete access

• Endpoints of U.S. Highway 138
• Colorado Highways: Routes 120 to 139
• The Nebraska Highways Page: Nebraska Highways 101 to 300
• Nebraska Roads: Nebraska US Highways 136-183

Browse numbered routes
← SH 136	CO	→ SH 139
← N-137	NE	→ US 159