Forest Hill is an unincorporated community in Harford County, Maryland, United States, located north of the county seat of Bel Air. The main part of town is located at the intersection of Maryland Route 24 and Jarrettsville Road. Until 1958, this community was served by the Maryland and Pennsylvania Railroad at milepost 30.3. Forest Hill's ZIP code area covers a relatively large area, with rural land on one side and suburban neighborhoods on the other.