The Llano Roadhouse is an excellent example of the Greek Revival farmhouses built by early settlers in Sonoma Valley. All lumber was hand milled: hand-hewn timbers, hand-split siding, hand-planed windows. The construction method is similar to colonial American construction before the advent of balloon framing.

The original one-story part of the building dates to the early 1850's. The two-story section was added around 1857 when the building became a roadhouse for the stage coach between Petaluma and Sebastopol.