The Smithsonian has an amazing horticulture division that until recently I didn’t know existed. You should take some time to look through their webpage and see what all they have. One of the things that I found really interesting was the ‘Archives of American Gardens.’ Here is their “mission statement”……
The Archives of American Gardens (AAG), founded in 1987, offers landscape designers, historians, researchers, and garden enthusiasts to approximately 80,000 photographic images and records that document a wide variety of historic and contemporary gardens throughout the United States.
The mission of the Archives of American Gardens is “to collect and make available for research use unique, high quality images of and documentation relating to a wide variety of cultivated gardens throughout the United States that are not documented elsewhere since historic, designed and cultural landscapes are subject to change, loss and destruction. In this way, AAG strives to preserve and highlight a meaningful compendium of significant aspects of gardening in the United States for the benefit of researchers and the public today and in the future.”
There are some really great images that they have available on Flickr, I have posted some of them here for you. These are all old glass lantern slides from the 1920’s and 30’s.