Where are the underground tunnels built by masons in New York City and Boston in 1760's~1780's? Do they exist till our present day?
I've found something:
Originally, the small building was known as Goff’s Tavern and was rumored to have secret tunnels to which the local English-sympathizing Tories would repair for escape from the Patriots. Later, runaway slaves allegedly used them during the Civil War. So far, those tunnels haven’t been confirmed, but additional archeological digs are planned.
However, it appears this info was copied directly from another article(warning: large file) which goes into much deeper detail about the tavern. However, it says no more about the tunnel. It does not say when the building was constructed, but it does allude to the late 1700s. It is found in Monroe, New York. It could be what you're looking for.