Two miles east of Pasco [1] off Highway 12, Sacajawea State Park (509/545-2361, www.parks.wa.gov [2], 6:30 a.m.–dusk Wed.–Sun. April–Sept.) sits at the confluence of the Snake and Columbia Rivers at the site where Lewis and Clark camped in 1805 on their way to the Pacific Ocean. You can fish, water-ski, or picnic here; there is no camping.
An interpretive center (1–5 p.m. Fri.–Tues.) contains exhibits on Sacajawea—the Shoshone woman who acted as interpreter for the Lewis and Clark party—plus information about the expedition, videos, and Native American artifacts.
Links:
[1] http://www.moon.com/destinations/washington/columbia-gorge-and-wine-country/tri-cities
[2] http://www.parks.wa.gov