Author Susan La Riviere has written several (fiction) books based on Yakima.

The Lords of Moxee (a Romeo & Juliet replacing Montegues and Capulets with French farmers and Mexican Laborers)

Wolf Castle (fictionalizes Congdon Castle)

Ghost of the Capitol Theatre

And the non fiction St. Joseph's on Fire

Historical non-fiction could be Little War of Destiny which covers the Yakama/Walla Walla Indian war, Unsettled Ground: The Whitman Massacre and it's Shifting Legacy in the American West, Murde and Mayhem in Central Washington, Hidden History of Yakima.

Visiting local museums can also help. Prior to WWII agricultural areas were home to a lot of Japanese, Phillipino, and other Asian immigrants and Americans. After the WWII internment, most of them never returned.

There are a lot of long-rooted families in the area, particularly in the farmlands.

I'm kind of double-rooted. Through French-Canadian immigrant roots (my great-uncles were dentists in town, and my grandfather ran a grocery store - the building was a barbershop for decades and is now I think residential), his cousin also ran a grocery store until about 20 years ago. On my mother's side I am Yakama Native and a descendent of two generations of Chemawa children. My great-great grandfather was charged with assault and attempted murder for fighting the BIA agents when they came to take his kids. Actually coming down to the last of the line on the paternal side, as all my dad's siblings moved away and all my siblings moved away.

Aaaaaanyway. Short info and resources for you.