I've been looking up some Web sites for the places mentioned above:

Here is the James Rumsey Monument in Shepherdstown, WV, which may have been what Naemanson was describing. Also here is A Short Treatise on the Application of Steam, dated 1788, by Rumsey himself. (OK, maybe nobody here wants to read this, but I find it so amazing just to know that such things exist on the Internet, that I can't help sharing my fascination.)

Kim C mentioned the Sam Davis Home in Smyrna, TN.

Sharon A mentioned The Pearl S. Buck House, in Hilltown Township (Bucks County), PA., The Henry Chapman Mercer Museum in Doylestown, PA (which also has a folk festival), and whose site contains links to Fonthill, I also found The James A. Michener Art Museum in Doylestown, PA -- but I was unable to find any information about his house.

Dave the Gnome mentioned the Wet Earth Colliery, Clifton, Manchester, UK.

I'm guessing Gloredhel was describing the Carnegie Museum in Roseville, CA. (If not, it's an amazing coincidence.)

Rick Fielding mentioned the Bata Shoe Museum and Old Fort York, both in Toronto, ON, Canada.

That's enough for now. Maybe I will post more later.