U.S. Highway 18 (US 18) is an east–west United States Numbered Highway in the Midwestern United States. The western terminus is in Orin, Wyoming, at an interchange with Interstate 25 (I-25). Its eastern terminus is in Downtown Milwaukee, Wisconsin. US 18, however, runs concurrent with other U.S. Highways from its western terminus to Mule Creek Junction, Wyoming. US 18 is one of the original U.S. Highways of 1926. The US 18 designation was originally proposed for a road in Michigan from Grand Haven east to Detroit. This roadway was eventually designated as US 16.

Interstate 25 (I-25), also known as the Pan-American Freeway, is a major Interstate Highway in the western United States. It is primarily a north–south highway, serving as the main route through New Mexico, Colorado, and Wyoming. I-25 stretches from I-10 at Las Cruces, New Mexico to I-90 in Buffalo, Wyoming. It passes through or near Albuquerque, New Mexico; Pueblo, Colorado; Colorado Springs, Colorado; Denver, Colorado; Fort Collins, Colorado; and Cheyenne, Wyoming. The I-25 corridor is mainly rural, especially in Wyoming, excluding the Albuquerque metropolitan area and the Front Range urban corridor from Pueblo to Cheyenne.