Harford County, in northeastern Maryland, lies between Pennsylvania and the Chesapeake Bay. It was formed from Harford County in 1773. The northern four-fifths of the county lies in the Piedmont Plateau and has an elevation of 200 to 750 above sea level. The southern one-fifth is part of the Coastal Plain and is 40 to 200 feet above sea level. About a third of the county is devoted to agriculture.
Harford County gets its name from Henry Harford, son of Frederick Calvert, the 6th and last Lord Harford. Concord Point Lighthouse is the oldest continually used lighthouse on the East Coast. The county seat is Bel Air.