From the record
“The Historic Columbia River Highway is an approximately 75-mile-long (121 km) scenic highway in the U.S. state of Oregon between Troutdale and The Dalles, built through the Columbia River Gorge between 1913 and 1922. As the first planned scenic roadway in the United States, it has been recognized in numerous ways, including being listed on the National Register of Historic Places, being designated as a National Historic Landmark by the U.S.”
Wikipedia article Historic Columbia River Highway, CC BY-SA 4.0.
One of 650 National Register listings published here for Multnomah County · listed in 1983 · category: District · a National Historic Landmark.
Sources: the Wikipedia article · the case file at the National Archives · the National Register database, National Park Service