A rare Pend Oreille River drawdown behind Boundary Dam reached its low point last fall, exposing Metaline Falls for the first time in 27 years. In the morning of Sept. 20, 2011, the drawdown is set to be repeated for another work project at Boundary Dam. Canadian explorer and fur trader David Thompson scouted the area in 1812 looking for a shorter route to the Columbia River for the North West Company’s fur trade. Thompson found the river at Metaline Falls and downstream at Z Canyon to be enclosed by steep rock cliffs and boiling with whitewater. He concluded it was impassable, and turned back. Completion of Boundary Dam in 1967 changed the nature of the canyon. Here are photos from the September 2010 drawdown to give viewers a glimpes of what's in store Tuesday. The photos are matched with historic photos from The Spokesman-Review archives.