Redstone Arsenal (RSA) is a United States Army post and a census-designated place (CDP) adjacent to Huntsville in Madison County, Alabama, United States and is part of the Huntsville-Decatur Combined Statistical Area. The Arsenal is a garrison for a number of tenants including the United States Army Materiel Command, Army's Aviation and Missile Command, the Missile Defense Agency of the Department of Defense, and NASA's Marshall Space Flight Center.