[citation needed] The drop off from the Plains to the Piedmont is noticeable to motorists driving southward from Cheyenne, Wyoming on Interstate 25.
At approximately Mile 293 northeast of Wellington, Colorado, near the Larimer-Weld county line, the road drops noticeably from the Upper Cretaceous sandstone of the Plains to the lower shale of the Piedmont.
[citation needed] In the 19th century, the Piedmont region was inhabited primarily by the Southern Arapaho and Cheyenne tribes.
From the earliest time of white settlement in the middle 19th century, the issue of water has been a controlling force in the economy of the region.
[citation needed] The use of irrigation in the Piedmont starting in the 1860s led to widespread homesteading and cultivation of wheat and sugar beets, as well as cattle and sheep ranching.