I haven't paid much attention to the uses of specific structures until recently - I was interested more in the general geography and things that photograph well. A few that come to mind (and I'm sure that there are many more...) are the South Mountain Inn, west of Frederick, Maryland, this Inn, in Flintstone, Maryland, and this place, which clearly requires some major work. There's also the Four Mile House, in Cumberland, and I'm sure many more.
One of the more interesting ones is on an old alignment, Exline Road, on the east side of Sideling Hill, a couple miles west of Hancock, Maryland. I can't quite tell whether it's been split up into a triplex or what. I'll post photos later tonight, once I figure out how to fix all the photos that I shot with the white balance on my camera set to "tungsten" - oops.
Unlike in, say, Ohio, where many of the National Road motels have remained motels or rental housing, many of the inns in Maryland have become private houses. You notice them mostly because a house seems both too big and too close to the road for the age of the structure - if it were merely the house of a well-off individual, it would be set back further from the road.