Since it was mentioned in another thread, I've been gradually re-reading
Iron in the Pines. Pierce writes quite a bit about the town of Washington and the tavern. This part might be of interest, and he also writes about the other ruins - see pages 63-66. Pierce liked long sentences.
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"The location of the famous tavern was for a long time a mystery. Its cellar is to be found precisely where some old maps show it to have been: three-tenths of a mile east of the ruin which was not a tavern, at a crossroads where another trail - once another stage road - led from the Eagle Tavern, above Speedwell, almost directly south to what once was Upper Bank and what is Green Bank today. At this junction, almost overgrown, are the remains of the old basement and wine cellar. This identification is not based on guesswork, hearsay, or legend, but upon the old deeds, which describe the 'place known by the name Washington Tavern in the Township of Washington ... on the road leading from Tuckerton to Philadelphia by the Mail Stage Route' and locate one corner of the property as the 'middle of the road from Washington Taven to the Bank [Green Bank].'"