Washington County, Maryland is included in the Hagerstown-Martinsburg, MD-WV Metropolitan Statistical Area, which is also included in the Washington-Baltimore-Arlington, DC-MD-VA-WV-PA Combined Statistical Area. The closes states to Washington County is west Virginia, Pennsylvania, Virginia, and Tennessee. The western portions of the Province of Maryland (including present Washington County) were incorporated into Prince George's County in 1696. This original county included six current counties. The first to be created was Frederick, separated from Prince George's County in 1748. Following independence, the sovereign State of Maryland formed Washington County on September 6, 1776, by the division of Frederick County. At the same time, a portion
Montgomery County, Maryland Montgomery County, Maryland Montgomery County is the most populous county in the U.S. state of Maryland, located adjacent to Washington, D.C. As of the 2010 census, the county's population was 971,777, increasing by 9.0% to an estimated 1,058,810 in 2017. The county seat and largest municipality is Rockville, although the census-designated place of Germantown is the most populous place. Montgomery County is included in the Washington–Arlington–Alexandria, DC–VA–MD–WV Metropolitan Statistical Area, which in turn forms part of the Baltimore–Washington Combined Statistical Area. Most of the county's residents live in unincorporated locales, of which the most built up are Silver Spring and