Fort Mason was established on July 6, 1851, in present-day Mason County, Texas. It was named in honor of George Thomson Mason, a United States Army second lieutenant killed in the Thornton Affair during the Mexican–American War near Brownsville, April 25, 1846. At various times from 1856 to 1861, this was the home fort for Albert Sidney Johnston, George H. Thomas, Earl Van Dorn, and Robert E. Lee. The fort was abandoned by the military in the 1870s, and restored by a group of local citizens in 1975. Visitors can tour the reproduction officers' quarters at the Fort Mason Museum.

The 5th Cavalry Regiment is a historical unit of the United States Army that began its service on August 3, 1861, when an act of Congress enacted "that the two regiments of dragoons, the regiment of mounted riflemen, and the two regiments of cavalry shall hereafter be known and recognized, as the first, second, third, fourth, and fifth regiments of cavalry respectively..." and continues in modified organizational format in the U.S. Army.