Bonneville Dam snakes across the Columbia in three sections, connecting the shorelines and Bradford and Cascades Islands. This was the site of the famous Columbia River Cascades that made travel down the river so treacherous for Oregon Trail emigrants.
An Army base, Fort Cascades, was constructed on the Washington side of the Cascades in the early 1850s and remained in use until 1861. Today, Fort Cascades Historic Site has an interesting 1.5-mile loop path with interpretive signs describing the area’s rich history.
The original Bonneville dam and power plant were built here between 1933 and 1937; a second plant was added on the Washington shore in 1981. Together they produce over a million kilowatts of power that feed into the grid for the Northwest and California.
Visit the Bonneville Second Powerhouse visitors center (509/427-4281, 9 a.m.–5 p.m. daily, closed major holidays), on the Washington side of the Bonneville Dam, to see the inner workings of the powerhouse (including a peek inside a spinning turbine) and informative displays.
You’ll feel dwarfed by the enormity of the river, dam, and surrounding hills. Windows offer a chance to watch coho, sockeye, and king salmon, along with steelhead, shad, lamprey, and other fish as they head upstream each summer and fall.
Cross The Bridge of the Gods  ($1 toll for autos) into Oregon and visit the original Bonneville Lock and Dam (541/374-8820), a popular tourist spot with continuous presentations, exhibits, and fish viewing.