   washington county is a county located in the western part of the u.s. state of maryland. as of the 2010 u.s. census, the population was 147,430. its county seat is hagerstown. washington county was the first county in the united states to be named for the revolutionary war general (and later president) george washington. the county borders southern pennsylvania to the north, northern virginia to the south, and the eastern panhandle of west virginia to the south and west. washington county 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. washington county has experienced a population boom, and is one of the fastest growing counties in the country, due to an influx of people from washington and baltimore. ==history== the western portions 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. washington county was formed on september 6, 1776 by the division of frederick county. at the same time, montgomery county was also separated from frederick county and was named for general richard montgomery. washington county as created included land later to become [[allegany county, maryland|al
1776_establishments_in_Maryland Counties_of_Appalachia Hagerstown_metropolitan_area Maryland_counties Maryland_counties_on_the_Potomac_River Populated_places_established_in_1776 Washington_County,_Maryland