Western Maryland is the portion of the U.S. state of Maryland that traditionally consists of Washington, Allegany, and Garrett counties, with western portions of Frederick County also associated with the area. The region is bounded by the Mason-Dixon line to the north, Preston County, West Virginia to the west, and the Potomac River to the south. There is dispute over the eastern boundary of Western Maryland. For most residents of the Baltimore-Washington area, everything west of Frederick city is considered Western Maryland. However, the people of the more mountainous and isolated Allegany County and Garrett County consider Sideling Hill the boundary between Western Maryland and what they refer to as "down-state."