Massacre Rocks State Park is located along the Snake River west of American Falls, Idaho. It contains a configuration of boulders along the south bank of the Snake, known alternatively as Massacre Rocks, "Gate of Death," or "Devil's Gate."Massacre Rocks was a well-known site on the Oregon Trail and California Trail during the mid-19th century. Immigrants gave the name Massacre Rocks to the trail's narrow passage through the rocks. The name stemmed from the fear of a possible ambush by Indians.The pages of some immigrants' diaries indicate that settlers in five wagons clashed with the Shoshoni just east of the rocks, on August 9 and 10, 1862. The skirmishes actually took place east of the park, and not at Devil’s Gate as is commonly believed, but the undeserved name stuck.Geologically the park was created during the repeated volcanic activity on the Snake River Plain. The rocks were deposited in their present location at the end of the last ice age some 14,500 years ago, during the catastrophic deluge known as the Bonneville Flood, when most of Lake Bonneville surged down the Snake River.The rocks are all that is left of an extinct volcano; they were often used as campsite for wagon trains along the trail. The passage through the rocks is now the route of Interstate 86 along the south edge of the park.