Orangeville Rise is a major natural spring in Orange County, Indiana, near Orangeville and the second largest spring in the state. Protected as a National Natural Landmark since June 1972, it emerges from the karst landscape of the Mitchell Plain and drains about 48 square miles of dissolved limestone terrain to the northeast. Though sometimes linked with the Lost River, its water is not that river’s reappearance, which surfaces about 2 miles to the south. The spring is especially notable for its rapid response to weather, with storm discharge arriving in less than 24 hours after rainfall. It is owned and managed by The Nature Conservancy and the Indiana Karst Conservancy.