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The Layers of Portland Arch, F5007
There are over 280 Nature Preserves in Indiana, but the one that has largest natural bridge is Portland Arch.  The preserve, which now consist of 435 acres, was purchased from the Boy Scouts by The Nature Conservancy in 1966 and is today owned and managed by the Indiana DNR.  A small tributary of Bear Creek in rural Fountain County slowly carved into the Mansfield Sandstone laid down 230 million years ago.  The layers and textures of the sandstone walls provide a geologic marvel as you walk around the short .8-mile trail that leads through the Arch.<br />