The California Heritage Project is a digital archive containing photographs, pictures, and manuscripts from the collections of the Bancroft Library. Navigating through the huge collection takes some practice. One example of the material available is the collection of 38 pencil California Mission Sketches by Henry Miller in 1856. The American Memory Collection from the Library of Congress has photographs, prints, documents, motion pictures, and sound recordings.
Additional viewers are available for the sounds and movies.
One example of the type of material available is the Letter from S. Shufelt, a gold miner writing to a cousin from Placerville, California, in October 1850. A Changing State has resources and activities by unit. The San Francisco Museum's History site has indexes sorted by subject or year. The California Mission History website has a basic and more extensive essay on each mission with photographs, drawings, and pop-up definitions of words your students might not know. The California Missions website covers all 21 missions.