Built as an artillery fort by Colonel Hill in 1650 (William of Orange stayed here on his way to the Boyne in 1690), Hillsborough Fort was remodelled as a Gothic-style tower house in 1758. A tree-lined path opposite the Courthouse leads to the fort, which sits on the edge of Hillsborough Forest Park. Only the grounds are open to the public.
In 1771 Benjamin Franklin spent five days at the fort as the guest of Wills Hill, then Secretary of State for the Colonies. Reportedly the meeting went so badly that it helped convince Franklin that revolution was America's only option.