One of the two remaining forts in old Bangkok, Fort Phra Sumen was constructed in 1783 to fortify the old city during the reign of King Rama I. When Bangkok was established as the new capital, forts were built to cover the Chao Phraya River. The defensive rings of canals protected the old city to the east.
The fort is sited at the confluence of the Chao Phraya River and the Banglamphu Canal which was the second ring of canals to be built around the old city of Bangkok in 1782. The first canal was Lod Canal just east of the Grand Palace.