A brief history of the Texas Military Department. The 45,000-square foot Texas Military Forces Museum explores the history of the Lone Star State’s militia and volunteer forces from 1823 (date of the first militia muster in Stephen F. Austin’s colony) to 1903 when the Congress created the National Guard. From 1903 to the present the museum tells the story of the Texas Army and Air National Guard, as well as the Texas State Guard, in both peacetime and wartime. The Texas Military Forces Museum is located in Building 6 on Camp Mabry in Austin, Texas. Admission to the museum is always FREE.