Elephant Butte is a summit in Sierra County, New Mexico, now located within Elephant Butte Reservoir in Elephant Butte Lake State Park. Rising to 4,639 feet, it was originally a tall butte on the east bank of the Rio Grande and took its name from an outline said to resemble an elephant. Construction of Elephant Butte Dam flooded the surrounding area and turned the butte into an island, while more recent lower water levels have made it a peninsula again. The site is also notable for a nearly complete 3-million-year-old stegomastodon fossil discovered there by campers on June 9, 2014.