Most archives, historical societies, and genealogical societies have special collections and indexes of genealogical value. These must usually be searched in person.
A notable genealogical collection is the Daughters of the American Revolution (DAR) Collection. This collection consists of transcripts of Bible, cemetery, church, marriage, death, obituary, and will records. It was microfilmed in 1971 at the DAR Library in Washington, D.C., and is available on 33 reels at the Family History Library (beginning on FHL film 857012). The volumes are generally arranged by county, and many have individual indexes.
There are many internet articles on the history of Oregon on the internet. To find some of them use a search engine with the terms Oregon and History.