Coulee City and the World's Biggest Waterfall (Dried Up)

Just south of Coulee City lies Dry Falls, the remains of what geologists believe was once the largest waterfall on Earth. During the last Ice Age, ice dams on the Clark Fork and the Columbia sent cataclysmic Missoula floods surging across the Columbia Plateau. The floodwater cascaded four hundred feet over a ledge three and a half miles wide, with a flow scientists estimate at ten times the combined discharge of all rivers in the world today.

Then the ice retreated, the river found its old channel, and the falls went dry. What's left is a breathtaking basalt amphitheater with nothing in it but wind. Today the farmland around Coulee City is irrigated by water pumped from Grand Coulee Dam, transforming Ice Age flood plain into some of Washington's most productive farmland.