Washington County Maryland, 457.78 square miles as of 2010, with an estimated population about 150,000. There are nine incorporated towns, and the City of Hagerstown along with roughly 47 other CDP and unincorporated.
Boonsboro and Keedysville seem to be having the most projected growth in the area as shown here
Lets not repeat what is out there. Here are some helpful links to the population and economics of the area.