Roll On, Columbia, Roll On near Cascades Rapids, in The Dalles, and on Memaloose Isle. The final three verses describe the construction of two Columbia River dams: Bonneville Dam and Grand Coulee Dam. Bonneville Dam, the first dam built on the Columbia, had locks built into it so ships could navigate past it, alleviating worries that a dam would prevent the shipment of goods and passengers along the length of the river. Guthrie's lyrics describe Grand Coulee Dam as "the mightiest thing ever built by a man"; when it was built it was the largest concrete dam in the world, and as of 2012 it
Columbia River known as the Grand Coulee. After the floods, the river found its present course, and the Grand Coulee was left dry. The construction of the Grand Coulee Dam in the mid-20th century impounded the river, forming Lake Roosevelt, from which water was pumped into the dry coulee, forming the reservoir of Banks Lake. The river flows past The Gorge Amphitheatre, a prominent concert venue in the Northwest, then through Priest Rapids Dam, and then through the Hanford Nuclear Reservation. Entirely within the reservation is Hanford Reach, the only US stretch of the river that is completely free-flowing, unimpeded by dams