The fort was originally constructed in 1864 as the Simanggang Fort after the victory of Charles Brook over Rentap. The fort was listed as historical monument by the Sarawak State Government in 1971. In June 2013, restoration works began on the fort and was completed on 18 April 2015 with a cost of MYR5 million. It was then reopened as the Sri Aman Heritage Museum.
The rectangular fort was built on a hilltop. It is equipped with cannons, open courtyard, drawbridge and lookout tower. The 150-year-old fort built in 1864 in Sri Aman – then called Simanggang – is a legacy of the white rajahs who ruled Sarawak.