The United States Naval Academy (also known as USNA, Annapolis, or simply Navy) is a four-year coeducational federal service academy in Annapolis, Maryland, United States. Established in 1845 under Secretary of the Navy George Bancroft, it is the second oldest of the United States' five service academies, and educates officers for commissioning primarily into the United States Navy and United States Marine Corps. The 338-acre (137 ha) campus is located on the former grounds of Fort Severn at the confluence of the Severn River and Chesapeake Bay in Anne Arundel County, 33 miles (53 km) east of Washington, D.C. and 26 miles (42 km) southeast of Baltimore. The entire campus is a National Historic Landmark and home to many historic sites, buildings, and monuments. It replaced Philadelphia Naval Asylum, in Philadelphia, that served as the first United States Naval Academy from 1838 to 1845 when the Naval Academy formed in Annapolis.