From the record
“The Grand Coulee Bridge, or Columbia River Bridge at Grand Coulee Dam, is a through-cantilever steel truss bridge built in 1934-35. It carries State Route 155 across the Columbia River immediately below Grand Coulee Dam, near the city of Grand Coulee, Washington.”
Wikipedia article Grand Coulee Bridge, CC BY-SA 4.0.
One of 16 National Register listings published here for Okanogan County · listed in 1982 · category: Structure.
Sources: the Wikipedia article · the case file at the National Archives · the National Register database, National Park Service