Aberdeen is a city located in Harford County, Maryland, United States, 26 miles northeast of Baltimore. The population was 16,254 at the 2020 United States Census. Aberdeen is the largest municipality in Harford County. Aberdeen is part of the Baltimore-Towson Metropolitan Statistical Area, which is the 20th-largest United States metropolitan area. The nearest city to Aberdeen is Havre de Grace, 4.8 miles to the northeast.