EAGLEVILLE, Pa.  A local planning board has approved a proposal to build a $250 million visitor center and conference facilities on privately owned land in Valley Forge National Historical Park. Opponents say the decision increases the risk of commercial development in other scenic and historic national parks.

The Planning Commission of Lower Providence Township, about 15 miles northwest of Philadelphia, voted unanimously late Wednesday in favor of the project, the American Revolution Center.

The center, on 78 acres inside the park, will include a 142,000-square-foot museum commemorating the American War of Independence, a 145,000-square-foot conference complex with as many as 99 rooms for overnight guests, and parking for 600 cars.

The center was conceived by the Valley Forge Historical Society to be the first national museum dedicated to the process of independence from Great Britain. It would be close to where Gen. George Washington’s troops camped during the winter of 1777-78, the period commemorated by the park.