Anne Arundel County is a county located in the U.S. state of Maryland. It is named for Anne Arundell (1615–49), a member of the ancient family of Arundells in Cornwall, United Kingdom and the wife of Cæcilius Calvert, 2nd Baron Baltimore. Its county seat is Annapolis, which is also the capital of the state. As of the 2010 census, its population was 537,656, a population increase of just under 10% since 2000.
Anne Arundel County forms part of the Baltimore-Washington metropolitan area. The center of population of Maryland is located on the county line between Anne Arundel County and Howard County, in the unincorporated community of Jessup.
The county was named for Anne Arundell, the daughter of Thomas Arundell, 1st Baron Arundell of Wardour, members of the ancient family of Arundells in Cornwall, England. She married Cæcilius Calvert, 2nd Baron Baltimore in 1627 or 1628.
Anne Arundel County was originally part of St. Mary's County in the Province of Maryland. In 1650, the year after Anne Arundell's death, the county separated and became the 3rd of 23 Maryland counties. Between 1654 and 1658, the county was known as "Providence County" by many of its early Puritan settlers.
On March 25, 1655, during the English Civil War, the Battle of the Severn was fought in Anne Arundel County between Puritan forces supporting the Commonwealth of England and forces loyal to Cæcilius Calvert. The Commonwealth forces under William Fuller were victorious.
During the American Revolutionary War, citizens of Anne Arundel County supported the Continental Army by providing troops for three regiments. The 3rd Maryland Regiment, the 4th Maryland Regiment, and the 6th Maryland Regiment recruited in the county.
On May 22, 1830, the inaugural horse-drawn train of the B & O Railroad travelled the of the newly completed track from Mount Clare Station in Baltimore City to Ellicott Mills in Anne Arundel County. This was the first regular railroad passenger service in the United States. In 1831, Land west of the railroad was considered the Howard District of Anne Arundel County. In 1851, The Howard district was broken off to form Howard County, the 21st county in Maryland.
The county has a number of properties on the National Register of Historic Places.