13 is, in the grand course of things, peanuts. Oregon managed to neatly sidestep the Civil War just a bit more than a decade later.
If you want lots of violent bloodshed, think of the Yankees colonizing the CSA. My great-great Grandmother is buried in Salem, and is remembered by her surviving grandchildren (and was remembered by the deceased ones) as a very bitter woman. She grew up in Southern Missouri in the 60’s—she and Martha Ellen Young Truman would likely have shrugged the Whitman Massacre off.
And talking to my parents (who say that my Grandfather, who was a member of the Society of the Native Oregon Born [SNOB] is turning in his grave). He would belt the song out whenever he crossed into the state.
And FWIW—the Whitman Massacre happened in the part of Oregon territory that would become Washington. But you take what you can get.