Discovery Center and the dam in The Dalles
Two public places tell the story of The Dalles and the river. Both keep their own hours, so check before you go.
Columbia Gorge Discovery Center and Museum
The Columbia Gorge Discovery Center is a museum at 5000 Discovery Drive in The Dalles. Its website calls it the Official Interpretive Center of the Columbia River Gorge National Scenic Area and says its mission is "to inspire stewardship of the Columbia River Gorge and Wasco County," including the preservation, collection and interpretation of the region's cultural and natural history. The site lists daily hours of 9 am to 5 pm. It has an exhibitions section, an events list and an Oregon Trail collection under its research pages. Admission, programs and hours are posted on the museum's site and can change.
The Dalles Dam
The Dalles Dam is run by the U.S. Army Corps of Engineers. Recreation.gov, which carries the Corps listing, says the dam is 192 miles upstream from the mouth of the Columbia River and that the project has a navigation lock, spillway, powerhouse and fish passage facilities. Lake Celilo behind the dam is 24 miles long, and the listing says there is a visitor center with exhibits on the project and the region and rangers on site.
Wikipedia says construction began in 1952 and the dam opened in 1957, and that the rising water submerged Celilo Falls in March 1957. Visitor center hours and tour availability change from year to year, so check with the Corps before you go.