Yakima is the main city of the Yakima Valley, a dry agricultural basin famous for apples, wine grapes, and hops. If you drink American craft beer, there is a good chance some part of it passed through this valley.
The city itself is practical rather than pretty, but it has enough for a worthwhile day. The Yakima Valley Museum tells the valley story well, the Yakima Area Arboretum gives you shade and trees in a dry landscape, and Yakima Sportsman State Park shows how much life irrigation brings to the river floodplain.
Yakima is also a gateway to wine touring, the Yakima River canyon, and the drier side of Washington State. It is worth stopping when you want to understand the state's agricultural engine rather than only its coast and mountains.