For years, when doing a library tour, I've stopped at our shelves of Life magazines. Our bound volumes on the third floor outside of the classroom start in 1936 and go through about 1983. Students are amazed at the history these represent--the articles, the advertisements and the photos. Google has gotten the Life photo collection from 1750s and made it available on their Images search. All those famous shots of presidents' inaugurations, presidents'funerals, war, wars' ends, fashion icons and the poor unfashionables.
To browse the collection go to Google, choose "Images" search and use these words: source:life.
To search it just add another word, for example: source:life vietnam.