This collection, assembled by the Oregon Historical Society Research Library, primarily consists of printed material that was either produced in or closely relates to the Oregon Territory and to Oregon's early statehood. Almost all of these items were listed in George Belknap's 1968 bibliography, "Oregon Imprints, 1845-1870."

The materials in this collection include legal and judicial documents such as legislative bills, reports, and proceedings; records of associations, including masonic organizations, temperance organizations, the Independent Order of Odd Fellows, and religious organizations; announcements and proclamations; event invitations, announcements, and programs, including for Fourth of July celebrations and the Oregon State Fair; advertisements; newspaper pages; and almanacs. The collection also includes some materials relating to conflicts between Euro-Americans and Native peoples, such as the Rogue River War of 1855-1856.

With some exceptions, materials are listed in this collection guide in numerical order based on numbers Belknap assigned to each item in his bibliography. Not all items that appear in Belknap's bibliography are included in this collection, and so some item numbers are skipped. Item numbers are typically handwritten on the documents themselves or on enclosing envelopes; sometimes these also show an earlier number that Douglas C. McMurtrie had assigned. The collection also includes a handful of items that were not cataloged by Belknap, but which also date from the mid-19th century.

Other materials in the collection include copies of Belknap's "Oregon Imprints, 1845-1870," supplements to "Oregon Imprints, 1847-1870" and to "Oregon Imprints, 1845-1870," and Belknap's correspondence and writings relating to early Oregon imprints.