National Park Service.
"At the end of the last Ice Age, some 12,000 to 17,000 years ago, a series of cataclysmic floods occurred in what is now the northwest region of the United States, leaving a lasting mark of dramatic and distinguishing features on the landscape of parts of the States of Montana, Idaho, Washington and Oregon." Public Law 111-11, March 30, 2009
From Spokane Take I-90 West At Exit 277, merge onto US-2 toward Davenport/Fairchild AFB/Spokane Airport Just past Wilbur, turn right onto WA-21 Stay left onto Highway 174 Turn right onto WA-155 Stay on WA-155 past Grand Coulee Dam and into the town of Coulee Dam Cross the Columbia River and continue on WA-155 Turn right onto Crest Drive and follow up the hill. The HQ Office is located on the left