Ok, I think the 'report' is the diary of sorts written by an immigrant. He talks of many things, and the report is available via the History of the Great Basin area and tribes.
I, probably mistakenly, thought the largest barrier to the Willamette Valley was the Nez Perce. Not that they were warlike but that being friendlies they were not quite so easy to rape.
'Not quite so easy' is a relative term. There were, thanks to our various Federal and local agencies, many ways to acquire what the tribes had that the whites wanted. The term 'Treaty' should be a curse word of the worst connotation.
Here is a link I perused. You probably know of it, but in case you don't.

http://www.idbsu.edu/history/issuesonline/fall2004_issues/3f_never.html