The Ayres Natural bridge is a true natural bridge, undercut by an active stream. It spans 150 feet over the stream at a height of 50 feet, the bridge itself approximately 20 feet thick.
Accessible just off Interstate 25 west of Douglas, Wyoming, the Ayres Natural Bridge and Ayres Natural Bridge Park are of geologic and historic interest. LaPrele Creek once made a long bend around an outcrop of very old sedimentary rock (300 million years old!) until the creek's upstream and downstream erosion of the ridge cut all the way through and created a natural passage - a natural bridge - through which the stream now flows.
Though only a few miles from the famous Oregon Trail, along which numerous emigrants traveled west during the pioneer days, the bridge was difficult to access. Only a few early explorers as well as a handful of California gold rush miners left records of having passed. A modern road now provides easy access to the bridge and public park.