Portland Arch Nature Preserve is a 435-acre protected area in western Indiana near the Wabash River, encompassing Bear Creek’s wooded valleys, ravines, and rocky cliffs. Recognized as a National Natural Landmark, it is named for a rare natural sandstone arch, one of only a few in Indiana, formed when Bear Creek undercut a bluff from both sides and left a standing span in Mansfield Sandstone. The rock dates to the Pennsylvanian Period about 230 million years ago, with layered sediments recording changing water depths. Native Americans and early pioneers used such arches as shelters, and the preserve is now managed by the Indiana Department of Natural Resources.

Williamsport, Indiana · USA