OER are teaching, learning, and research resources that reside in the public domain or have been released under an intellectual property license that permits their free use and re-purposing by others. ~ William & Flora Hewlett Foundation
For a more comprehensive overview on OER, see:
"Routes of the Underground Railroad, 1830-1865." See page for author [Public domain], via Wikimedia Commons. This work is in the public domain in the United States because it was published (or registered with the U.S. Copyright Office) before January 1, 1923.
This is a sample of several OER Multicultural History textbooks and course materials available. Additional OER may be found by searching the resources listed on the ACC Libraries primary Open Educational Resources Guide.