Casper, now Wyoming's second-largest city with a vibrant downtown, was called "the crossroads of the West" in pioneer times. The California, Mormon, Oregon, Overland and Pony Express Trails passed through, as documented by the National Historic Trails Interpretive Center.
A few miles east of I-25 is the Teapot Dome, the rock formation that lent its name to the biggest oil-fueled political scandal of the 1920s. Get closer via Hwy. 250 (Exit 210), a 25-mile loop that re-enters I-25. Kaycee (Exit 254) boasts a strong Western (and even Wild West) heritage. Butch Cassidy and the Hole-in-the-Wall Gang hid out nearby.

Today, this traditional farming and ranching community is also a gateway into the Powder River Basin. From there northward, increasingly magnificent mountains loom west of the freeway. I-25 ends when it joins Interstate 90 at Buffalo (Exit 300), splendidly situated just east of the Bighorn Mountains. Stop for the night.