[or-roots] Yamhill County search - Forrest, Clark, Sims, Lambert

[Suz_ES]

I am new to this list and would appreciate any help I can get.
I am working on the following:
Thomas Benton Clark m. Matilda Forrest in Dayton, Yamhill, Oregon 1876 or
1878.
Their son Riley Lester Clark m. Stella Irene Sims in Portland, Multnomah,
Oregon March 19, 1916.
Riley and Stella were my maternal grandparents.

I have more detailed information, but am looking for Thomas Benton Clark
ancestors or some indication why he was the only one of his family to move
to Oregon.

Thanks
Suzanne