Grand Gulf State Park
Canyon · Thayer, Missouri
A forked canyon near Thayer in the far south of Missouri that is the remnant of a dolomite cave system whose roof collapsed - about a mile of chasm up to 130 feet deep, with a natural bridge where a section of roof survived. A creek runs into it and disappears underground, resurfacing nine miles away across the Arkansas line at Mammoth Spring. It was declared a National Natural Landmark in 1971 as an example of karst topography and underground stream piracy, which is exactly what it is.
County Road 151, Thayer, Missouri, 65791, United States
FREE and open daily, generally dawn to dusk, year round. There is no visitor centre and the park is unstaffed most of the time. THE BOARDWALK AND OVERLOOKS ARE THE VISIT and are open whenever the park is. The gulf floods after heavy rain - water backs up in the canyon and the lower trail becomes impassable, sometimes for days. There is no camping.
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