As of 2015, the population of Anne Arundel County was 564,195. The population increased just under 10% since 2000. Its county seat is Annapolis which is also the capital of the state. The county is named for Lady Anne Arundell (1615–49), a member of the ancient family of Arundells in Cornwall, UK and the wife of Cecilius Calvert, second Baron and Lord Baltimore, (1605-1675), founder and first Lord Proprietor of the colony Province of Maryland.
As of the 2010 United States Census, there were 537,656 people, 199,378 households, and 139,262 families residing in the county. The population density was 1,295.9 inhabitants per square mile. There were 212,562 housing units at an average density of 512.3 per square mile. The racial makeup of the county was 75.4% white, 15.5% black or African American, 3.4% Asian, 0.3% American Indian, 0.1% Pacific islander, 2.4% from other races, and 2.9% from two or more races. Those of Hispanic or Latino origin made up 6.1% of the population. In terms of ancestry, 23.3% were German, 18.6% were Irish, 12.3% were English, 7.4% were Italian, 5.0% were Polish, and 4.4% were American.
Of the 199,378 households, 34.6% had children under the age of 18 living with them, 53.1% were married couples living together, 12.1% had a female householder with no husband present, 30.2% were non-families, and 23.7% of all households were made up of individuals. The average household size was 2.63 and the average family size was 3.11. The median age was 38.4 years. The median income for a household in the county was $83,456 and the median income for a family was $97,557. Males had a median income of $63,187 versus $48,750 for females. The per capita income for the county was $38,660. About 3.3% of families and 5.3% of the population were below the poverty line, including 6.9% of those under age 18 and 5.5% of those age 65 or over.
According to the U.S. Census Bureau, the county has a total area of 588 square miles, of which 415 square miles is land and 173 square miles (29%) is water. Anne Arundel County is located to the south of the city of Baltimore.