Great Falls Park is a small National Park Service site in Virginia, United States. Situated on 800 acres along the banks of the Potomac River in northern Fairfax County, the park is a disconnected but integral part of the George Washington Memorial Parkway. The Great Falls of the Potomac River are near the northern boundary of the park, as are the remains of the Patowmack Canal, the first canal in the United States that used locks to raise and lower boats.