Established March 13, 1847 as Alexandria County, the name was changed to Arlington on March 16, 1920. The county is named for the estate where George Washington Parke Custis lived before he built the house currently known as Arlington House in Arlington National Cemetery. The estate had been named to honor the Earl of Arlington.
The Arlington County Planning Division estimates that Arlington's population as of January 1, 2013 was 212,900.
In 2000, Arlington was the 13th most densely-population jurisdiction in the U.S. (7,287 persons per square mile.) As of January 1, 2013, the population density was 8,252 per square mile.
Arlington County has the highest percentage of people with bachelor's or graduate/professional degrees in the Washington DC area.
About 92% of all graduating high school seniors in Arlington County go on to attend college.
About 15% of Arlington County's population is Hispanic or Latino - the third highest percentage (after Prince William County and Loudoun County) in the Washington metropolitan area.
About 27% of Arlington County residents speak a language other than English at home.
The land area of Arlington County is 25.8 square miles and the highest point in the County is 461 feet above sea level.
Eleven of the eighty-six stations of the Washington Metropolitan Area Transit Authority's (WMATA) Metrorail system are located in Arlington. The Rosslyn Metro Station features one of the longest continuous escalators in the world (194 feet, 8 inches). It takes 140 seconds to ride from top to bottom.