Two more near-disasters on May 17 led to the naming of additional features. William Clark was nearly bitten by a rattlesnake while exploring a creek on the northern side of the river. This creek was named Rattlesnake Creek (although today it is called Timber Creek). The party camped near a creek on the south side of the river that evening. Clark saw a fortified Native American lodge a short distance up the creek, believing it to be an Atsina (Gros Ventre) site. Late that night, a cottonwood tree sheltering the camp caught fire from sparks rising from the expedition campfire. The men were barely able to get out of their tent and pull it out of the way before the tree came crashing down on the site. Lewis named this Burnt Lodge Creek (although today it is known as Seven Blackfoot Creek). On May 20, the expedition passed the Musselshell River. On May 22, the party passed another creek, which they decided to name Sacajawea Creek. (Later renamed Crooked Creek, the U.S. government formally changed the name back to Sacagawea Creek in 1979.) The Corps of Discovery left the CMR NWF on May 24 or 25, after spending a week passing through and exploring the area.