An early addition to the National Park Service (park #10), Glacier National Park in Montana turned 100 on May 11, 2010. The park is immense, with 1 million acres (4,047 km2), 300 lakes and a reach of 1,584 square miles (4,103 km2). The park is considered the centerpiece of a vast region of protected land that includes some 16,000 square miles (41,440 km2). The park features some 700 miles of hiking trails and supports all manner of outdoor activities, such as biking, boating, fishing, and horseback riding. There are 13 campgrounds that allow for roughly 1000 campsites. Other accommodation options include hotels, inns, lodges and motels. Part of Waterton-Glacier International Peace Park, this park has over 50 remaining glaciers and 130 named lakes under the tall Rocky Mountain peaks. There are historic hotels and a landmark road in this region of rapidly receding glaciers. These mountains, formed by an overthrust, have the world's best sedimentary fossils from the Proterozoic era.