More than 240 miles east of here, Silver Bow Creek tumbles west from the Continental Divide above Butte, Montana, beginning the Clark Fork River, which drains more than 22,000 square miles of western Montana before flowing into Idaho. Shortly before leaving Montana, its average discharge is greater than that of any other river in the state, and its waters eventually join the Columbia River, which drains much of the Pacific Northwest. The Clark Fork is harnessed to generate electricity by four dams at Milltown, Thompson Falls, Noxon Rapids, and Cabinet Gorge. The Salish people had different names for different places along the river to reflect its changing character and terrain, and trappers and fur traders called it the Missoula River because they floated it from that upriver city to the trading post at Thompson Falls. Its official name today is the Clark's Fork of the Columbia, though it is usually called the Clark Fork, and it is named for William Clark, who explored the western United States in 1805 and 1806 with Meriwether Lewis.