In reading the latest issue of the Old House Journal, I found an ad for Old House Live. In this online resource, the editor of the magazine has an online tour of historic sites and architectural treasures.
In the current posting, she tours Washington DC's Halcyon House, which was built in 1787 by Benjamin Stoddert, the first Secretary of the Navy, which is in the Georgetown area. See http://www.oldhouseonline.com/halcyon-house-video-tour-in-historic-washington-dc/
(The house pictured is also a 1780's house, in Magnolia, Delaware, which is much less sophisticated in this small town country location)
The Old House Journal is a good resource for all sorts of information and lots of articles about people who own historic homes and gardens. This website gives even more graphic proof of the value of this organization.