A National Park Service Historic Site since it was decommissioned in 1974, the Charlestown Navy Yard was one of six established to build warships. For 174 years, as wooden hulls and muzzle-loading cannons gave way to steel ships and sophisticated electronics, the yard evolved to meet the Navy's changing needs. Here are early-19th-century barracks, workshops, and officers' quarters; a ropewalk (an elongated building for making rope, not open to the public), designed in 1834 by the Greek Revival architect Alexander Parris and used by the Navy to turn out cordage for more than 125 years; and one of the oldest operational naval dry docks in the United States. The USS Constitution was the first to use this dry dock, in 1833. In addition to the ship itself, check out the Constitution Museum, the collections of the Boston Marine Society, and the USS Cassin Young, a World War II destroyer typical of the ships built here during that era. At the entrance of the Navy Yard is the Charlestown Navy Yard Visitors Information Center, with exhibits on ships and a fun little shop. A 10-minute movie about the Navy Yard runs every 15 minutes in a small theater.