The favorite local racing events are the hydroplane races during the Columbia Cup (509/547-2203).
At Kennewick’s [1] Benton-Franklin Fairgrounds, Sundowns Horseracing Track (E. 10th Ave., 509/582-5434) hosts quarter-horse racing in the spring and fall.
Links:
[1] http://www.moon.com/destinations/washington/columbia-gorge-and-wine-country/tri-cities