The south edge of the dam is located approximately 1/2 mile north of U.S. Route 56 on Old Mill Road, where there is an information kiosk and public restrooms.

In 1803, most of the land for modern day Kansas was acquired by the United States from France as part of the 828,000 square mile Louisiana Purchase for 2.83 cents per acre.

In 1855, Marion County was established within the Kansas Territory, which included the land for modern day Reservoir.

[5] In June and July 1951, the "Great Flood of 1951" occurred with a peak discharge of 54,000 cu ft/s (1,500 m3/s) and a volume of 78,950 acre-feet (97,380,000 m3) which is equivalent to 7.40 inches (188 mm) of runoff from the drainage area above the dam site.

In March 1964, construction was started on the Marion Reservoir, the embankment closure was completed in October 1967, and the project was placed in full flood control operation in February 1968.

Facilities at class "A" parks (Cottonwood Point and Hillsboro Cove) include electrical hookups, showers, RV dump stations, group camping areas, group picnic areas, playgrounds, and beaches.