U.S. Highway 87 (US 87) is a north–south United States highway (though it is signed east–west in New Mexico) that runs for 1,998 miles (3,215 km) from northern Montana to southern Texas, making it the longest north-south road to not have a "1" in its number and the third longest north-south road in the country, behind U.S. 41 and U.S. 1.

It merges with US-64 (and thus the Santa Fe Trail National Scenic Byway) in Clayton, shortly after entering New Mexico.

A portion of US-87 has been washed out for several years along this stretch and "temporary" detour signs are posted directing US-87 traffic along Wyoming Highway 193 through Story.

US 87 originally ran northwest out of Great Falls, Montana, towards the eastern border of Glacier National Park.

US 87 ended in Great Falls until circa 1945 when it was extended to its current northern terminus in Havre, Montana.

On March 15, 2022, a bill was signed by President Joe Biden that added the extension of I-27 from its termini in Amarillo and Lubbock, Texas, northward to Raton, New Mexico, and southward to Laredo, Texas, respectively to the Interstate Highway System utilizing the US 87 corridor.

[3][4] However, after legislation passed through the U.S. Senate in August 2023, I-227 and I-327 were respectively redesignated as I-27W and I-27N, with I-27E replacing the proposed I-27 between Sterling City and Lamesa.