U.S. #973 was issued in Prescott, Arizona, to commemorate the 50th anniversary of the formation of the Rough Riders. The 1st U.S. Volunteer Cavalry – later known as the Rough Riders – was formed in Prescott to fight in the Spanish-American War. While the Rough Riders are most often associated with Theodore Roosevelt, the stamp shows an image of William “Buckey” O’Neill.