Martinsburg is a city in the Eastern Panhandle region of West Virginia, United States. The city's population was 14,972 at the 2000 census; according to a 2008 Census Bureau estimate, Martinsburg's population was 17,020, making it the largest city in the Eastern Panhandle and the eighth largest municipality in West Virginia. Martinsburg is the county seat of Berkeley County and one of the core cities in the Hagerstown-Martinsburg, MD-WV Metropolitan Statistical Area. Martinsburg and Berkeley County are growing very rapidly from the influx of people moving from Washington, D.C. and Baltimore.