Photographs

• Explore Chicago Collections
• Library of Congress Prints and Photographs
• National Archives Photograph Collections
• Digital Commonwealth (Boston Public Library)
• Flickr Commons
• Wikimedia Commons
• New York Public Library Digital Collections
• Life Magazine Photos
• Ad Access (Duke University)
• Getty Images (Royalty free)
• The Public Domain Project

Videos

• Prelinger Archives (video)
• Internet Archive Moving Pictures
• National Archives YouTube Channel
• Library of Congress Digital Collections
• Library of Congress Screening Room

Will add more, send suggestions if you find any good resource!