Pulpit Rock Tower was one of several observation towers in the area built during World War II to search for enemy ships and airplanes. If any were spotted, the coordinates could be radioed to nearby Fort Dearborn (now Odiorne Point State Park) which had two rather large guns that could be trained on targets. This is one of the few remaining and the only one that is on public land. They open it for tours twice a year: on Memorial Day and Veterans’ Day weekends. You can see a video of the view from the observation deck here.