Fort de Chartres became Illinois' second state park, with restoration beginning in 1917 on the gun powder magazine after the state took ownership of the grounds in 1913. Further restorative work continued through the 1920's by uncovering the foundation, and in the late 1920's and through the 1930's the U.S. WPA rebuilt the land gate entrance and the two stone buildings that still stand. A road from Prairie du Rocher to the fort was built in 1919, and Illinois State Route 155 opened to traffic in 1929 after four years of construction, reflecting increased visitation to the fort and travel needs between the area and Ruma, Illinois. The site now serves as an attraction bringing 50,000 annual visitors to the area, with an estimated economic impact of $6,350,000 in 2022, and its gun powder magazine is the oldest building in the State of Illinois.