U.S. Route 400 is a 481.306-mile-long (774.587 km) mostly east–west U.S. Highway, commissioned in 1994. The highway's western terminus is in Granada, Colorado, at an intersection with US 385. The highway's eastern terminus is southwest of Joplin, Missouri, near Loma Linda, at an interchange with Interstate 44, with which it shares with US 166. It originally ended in Garden City, Kansas; in 1996 it was extended to its current western terminus.

Garden City is a city in and the county seat of Finney County, Kansas, United States. As of the 2020 census, the population of the city was 28,151. The city is home to Garden City Community College and the Lee Richardson Zoo, the largest zoological park in western Kansas.