quality:correction, structural:expansion
United States

In the early American Civil War the regular United States Army mounted rifle, dragoon, and two existing cavalry regiments were reorganized and renamed cavalry regiments, of which there were six. Over a hundred other federal and state cavalry regiments were organized, but the infantry played a much larger role in many battles due to its larger numbers, lower cost per rifle fielded, and much easier recruitment. However, cavalry saw a role as part of screening forces and in foraging and scouting. The later phases of the war saw the Federal army developing a truly effective cavalry force fighting as scouts, raiders, and, with repeating rifles, as mounted infantry. The distinguished 1st Virginia Cavalry ranks as one of the most effectual and successful cavalry units on the Confederate side. Noted cavalry commanders included Confederate general J.E.B. Stuart, Nathan Bedford Forrest, and John Singleton Mosby (a.k.a. "The Grey Ghost") and on the Union side, Philip Sheridan and George Armstrong Custer. Post Civil War, as the volunteer armies disbanded, the regular army cavalry regiments increased in number from six to ten, among them Custer's U.S. 7th Cavalry Regiment of Little Bighorn fame, and the African-American U.S. 9th Cavalry Regiment and U.S. 10th Cavalry Regiment. The black units, along with others (both cavalry and infantry), collectively became known as the Buffalo Soldiers. According to Robert M. Utley:

These regiments, which rarely took the field as complete organizations, served throughout the American Indian Wars through the close of the frontier in the 1890s. Volunteer cavalry regiments like the Rough Riders consisted of horsemen such as cowboys, ranchers and other outdoorsmen, that served as a cavalry in the United States Military.