Big John Access (also called Steelman Slab) is a Missouri Department of Conservation access point located on Highway 32 near Buffalo, providing entry to the Niangua River at approximately river mile 21. 5.

The access is situated at 968 feet elevation and serves as a convenient put-in or take-out point for paddlers and anglers, with no camping allowed at this location. This access point marks the downstream end of a 20.

3-mile reach that offers a quieter, less-crowded paddling experience with intermediate access points available upstream.