Base Quantico, within which the highway crosses Chopawamsic Creek into Prince William County. Immediately north of the county line, the route has a partial cloverleaf interchange with Russell Road, a major highway within the military base. US 1 passes the National Museum of the Marine Corps before its intersection at Triangle with SR 619 (Fuller Road), which leads east to the town of Quantico. At SR 619, US 1 leaves the base property and briefly expands to a six-lane divided highway, then splits onto separate carriageways—Fraley Boulevard northbound and Main Street southbound—to pass through the town of Dumfries, within which the U.S. Route crosses Quantico Creek. The carriageways reunite and US 1 meets the eastern end of SR 234 (Dumfries Road) at the northern limit of the town. The Dumfries Road Commuter Lot, a park-and-ride facility, is located north of this intersection. US 1 crosses Neabsco Creek into the large unincorporated area of Woodbridge near the Woodbridge Campus of Northern Virginia Community College. The U.S. Route meets the eastern end of SR 294 (Prince William Parkway) and begins to parallel the RF&P Subdivision rail line. US 1 passes Woodbridge station, which is served by Amtrak and Virginia Railway Express, shortly before its junction with SR 123 (Gordon Boulevard). The highway then crosses the Occoquan River into Fairfax County. US 1 continues as Richmond Highway through a partial interchange with I-95 at the southern end of Henry G. Shirley Memorial Highway. The interchange includes ramps from northbound US 1 to northbound I-95, southbound US 1 to southbound I-95, northbound I-95 to northbound US 1, and southbound I-95 to southbound US 1. At the north end of the interchange, US 1 passes under the RF&P Subdivision rail line and passes through the eastern fringe of Lorton, where it meets the northern end of SR 242 (Gunston Road). At Pohick Creek, the highway expands to six lanes and heads east and passes Pohick Church, then through Fort Belvoir. Within the military property, US 1 crosses Accotink Creek, meets the southern end of SR 286 (Fairfax County Parkway), and passes under an overpass of a road within the base. East of Fort Belvoir, the highway passes the historic plantation Woodlawn and the western end of SR 235 (Mount Vernon Memorial Highway), which leads to Mount Vernon. US 1 is reduced to a four-lane undivided highway before it crosses Dogue Creek and until it meets