18th century A portion was detached in 1748 to form Frederick County. Because Frederick County was subsequently divided to form the present Allegany, Garrett, Montgomery, and Washington counties, all of these counties in addition were derived from what had up to 1748 been Prince George's County.
18th century A portion was detached in 1748 to form Frederick County. Because Frederick County was subsequently divided to form the present Allegany, Garrett, Montgomery, and Washington counties all of these counties in addition were derived from what had up to 1748 been Prince George's County.