The Army formed a group of volunteers from the 25th Infantry, one of four African American regiments active from just after the Civil War through World War II.
As part of the testing, the 25th Infantry Bicycle Corps made several epic rides. They took nearly brakeless fixies (do spoon brakes count?) from Fort Missoula to Yellowstone in 1896 and went on a nearly 2,000 mile ride from Fort Missoula to St. Louis in 1897.
(Photo: Frank Jay Haynes at Northern Rockies Heritage Center)
The Northern Rockies Heritage Center has a nice overview from their time at Fort Missoula.
(Detail from Army History Journal [exact credit unavailable - click through for enlarged picture], but presumably from the University of Montana, Mansfield Library - see different print of same image here.)
Mike Higgins has blogged each day of the 1897 trip to St. Louis and has links to accounts of the other trips.
The next year, the Spanish-American war intervened and by the early 1900s, it was clear the automobile offered even more for troop movements and mobile gunnery.
Though it didn't last long, the Bicycle Corps is a fascinating episode of history in so many ways: Westward expansion, African-Americans and race relations, the technology of warfare.