Massacre Rocks derived its name from an emigrant wagon party skirmish. Register Rock, located two miles from the park, is home to a huge boulder that holds the signatures of Oregon Trail emigrants who stopped for an evening of rest before continuing on their journey. Today, Register Rock is a beautiful picnic area complete with shade trees, lawn, restrooms, fire pits, and barbecue grills.
The park is rich in geological history. Volcanic evidence is everywhere. The Devil’s Gate Pass is all that remains of an extinct volcano. The prehistoric Bonneville Flood shaped the landscape of the area, rolling and polishing the huge boulders found throughout the park. The flood was caused when eroding waters broke through Red Rock Pass near the Idaho/Utah border.
Lake Bonneville, which covered much of what is today the state of Utah, surged through the pass and along the channel of the Snake River in a few short months. For a time, the flow was four times that of the Amazon River. It was the second largest flood in the geologic history of the world.
Address: 3592 N. Park Ln
American Falls, ID 83211
Phone: (208) 548-2672
Hours of Operation: Day-use locations within state parks are open from 7 am to 10 pm, per Idaho state code 26.01.20 (5). Day-use hours may change based on park manager discretion.