Sharpshin Island

It is located less than a mile upstream (northwest) of Riley's Lock, which is Lock 24 on the C and O canal. Sharpshin Island itself is about two hundred yards long and very narrow, not more than fifty feet at its widest point. Like many of the islands on the Potomac, it usually has a flat beach at its head, a fairly open area, then denser foliage and trees toward the middle and to the foot. On the Maryland side, there is a small sandy beach about fifty feet downstream of the head that is a good place to land. Walking up to the middle of the island here reveals a small campsite complete with fire ring. The head of the island lies across from a boat ramp on the Virginia side; many power boaters and jet-skiers launch from here as well as Riley's. Dulles Airport is also fairly close, so you'll see plenty of planes flying across (usually north or south), but they're high enough not to be a nuisance.

Wikipedia