National Park Service, Washington.
At the end of the last Ice Age, 18,000 to 15,000 years ago, an ice dam in northern Idaho created Glacial Lake Missoula that stretched 3,000 square miles into Montana. The dam burst and released flood waters across Washington, down the Columbia River, back flooding into Oregon, before reaching the ocean. This happened perhaps a 100 times and changed the lives and landscape of the Pacific Northwest.
To Trail Headquarters 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