Check the A-Z Databases for a complete list.
Calisphere: California digital collections
"Calisphere provides free access to unique and historically important artifacts for research, teaching, and curious exploration. Discover over two million photographs, documents, letters, artwork, diaries, oral histories, films, advertisements, musical recordings, and more."
Digital Public Library of America
The Digital Public Library of America (DPLA) is a US project aimed at providing public access to digital holdings of images, texts, videos, and sounds from across the United States.