Big Springs State Park 2005

This is the largest spring in Missouri, the largest freshwater spring in the United States and one of the largest in the world. On an average day, around 278 million gallons of water gush forth from subterranean passages, swelling the nearby Current River. See 2004 pictures here.
Big Spring was one of Missouri's first state parks. It was a state park from 1924 until 1969 when the people of Missouri donated it, along with Alley and Round Spring State Parks to the National Park Service to become a part of the Ozark National Scenic Riverways. A gift from Missouri to America.