Tolo Lake, a shallow lake covering about 35 acres, is the largest natural water body on the Camas Prairie. It is a natural lake that has been enhanced to provide habitat for fish and waterfowl. The lake, 6 miles southwest of Grangeville, Idaho, is accessible via several unpaved section roads. To access the lake, take U.S. Highway 95 south out of Grangeville, Idaho, to the second road to the right past the Grangeville Country Club.
The Nez Perce name for Tolo Lake is Tepahlewam (Split Rocks). The lake, which is just east of Rocky Canyon, is an ancient rendezvous site the Nez Perce used for gathering foods such as camas root and for meeting with neighboring bands. Rocky Canyon was part of a transportation network in the area, connecting with the Salmon River and Snake River drainages.
Several nontreaty bands gathered here on June 2, 1877, in preparation for moving to the Nez Perce reservation. Angered by the forced move, several young Nez Perce decided to take revenge on some white men who had killed some of their people. As a result of this action and a second raid two days later, the 1877 Nez Perce War began. There is no interpretation at the site, but more than half of the interpretive sign for Camas Prairie is occupied by discussion of Tolo Lake's connection to the beginning of the war.
Significant remains of Pleistocene mammoth and prehistoric bison were excavated from the lake in 1994. To date, there has been no evidence of direct association of ancient humans with these remains. After the excavation was completed, the lake was allowed to return to its normal size.