Long, Stephen Harriman (1784–1864), a United States army engineer and explorer. In 1819–20 Major Long led an expedition to the Rocky Mountains. His party discovered Longs Peak in Colorado and gathered valuable information on the botany, zoology, and geology of the southern plains. In 1823 he led an expedition that explored the Minnesota River and the Canadian–United States border west of the Great Lakes.

Long was born in Hopkinton, New Hampshire, and graduated from Dartmouth College (1809). He joined the army engineer corps in 1814. After 1827 Long served as a consulting engineer for various railroads, becoming an authority on grades and bridges. He retired in 1863 as a colonel.