High Quality Content by WIKIPEDIA articles! National Harbor is a 300-acre (1.2 km2) multi-use waterfront development on the shores of the Potomac River in Prince George`s County, Maryland just south of Washington, D.C. near the Woodrow Wilson Bridge. It is being built by the Peterson Companies. The project is expected to cost over $2 billion. In addition to the Gaylord National Resort & Convention Center, which opened on April 1, 2008, National Harbor will contain five new hotels, waterfront condos, offices, retail stores, nightspots, a marina, and a new location for the National Children`s Museum.