One for the dominees.

Harvard's Francis Loeb library has this great collection of 2800 slides--actually they are lantern slides so don't expect full glowing colour--of American buildings and landscapes built between 1850 and 1920. It's at the rather cumbersome address http://memory.loc.govammem/ward97/mhsdhtml/aladhome.html and includes work of such as the son of F. L. Olmsted. There are estate maps, models, views of gardens plus a complete history of Boston's park system.