The United Mine Workers of America Building is an historic building at 900 Fifteenth St. NW in the Downtown neighborhood of Washington, D.C. Built in 1912 as the home of the University Club, a private social club, it was from 1936 to 1999 as the international headquarters of the United Mine Workers. Under the leadership of John L. Lewis, the union played a major role in improving working conditions and pay for a large number of mine workers, with Lewis eventually founding the Congress of Industrial Organizations to improve conditions for other types of laborers. The building was designated a National Historic Landmark in 2005. The upper floors of the building have been converted to residences.