I was unable to find out anything about the Wiscasset block house, but the tourist descriptions of Wiscasset was interesting.
Historic old sea captains' homes line the streets, shade trees and neatly-kept flowers and shrubs adorn the lawns. Wooden and brick storefronts serve to remind visitors of a village from 20 years ago. The name Wiscasset derives from the Indian phrase, "meeting place of the three rivers." The town overlooks the beautiful Sheepscot River, one of the deepest harbors in Maine. The first recorded settler was in 1660 when it was part of Pownalborough.
No information was provided on the blockhouse--perhaps it does not exist at this time.
The town was placed on the National Register of Historic Places, in 1973. Of interest to visitors are the Old Lincoln County Jail and Museum (1811) on Federal Street, the Castle Tucker House (1807), said to be haunted, the Carleton House (1804) and the Nickels-Sortwell House, a classic Federal-era mansion on High Street.