A few miles east of Glendo State Park lies a vast stone quarry initially mistaken for the work of early Spanish explorers. Archaeologists later determined the site, known as the Spanish Diggings, to be the work of various indigenous tribes on and off for the past several thousand years. Tools and arrowheads carved from the stone quarried here, including quartzite, jasper, and agate, have been found as far away as the Ohio River valley. To see the diggings you'll have to drive through Glendo State Park.
397 Glendo Park Rd., Lusk, Wyoming, 82213, United States