Grand Gulf State Park preserves one of the most spectacular geologic areas in Missouri. The major feature of the park is the collapsed remains of a major cave system, with a sinkhole, cave, natural bridge, and the gulf itself, which is often called the Little Grand Canyon.
The park, which is designated a National Natural Landmark, was acquired by the Missouri Department of Natural Resources in 1984 through a lease agreement with the L-A-D Foundation of St. Louis, owners of the property.

Historic Features
The geologic history of Grand Gulf began more than 450 million years ago when sediment was deposited by shallow seas, forming dolomite rock. As the land was uplifted, the waters receded. Water percolating through fractures in the rock slowly began to dissolve passageways. On the surface, streams began to carve down into the landscape.

As more water drained away, air-filled passages or caves were formed. Surface streams carved down through the rock and connected with the cave passage. In areas where the cave roof broke through, the stream was diverted or "pirated" underground.

As this process continued for thousands of years, more and more of the cave roof eventually collapsed. Geologists cannot say precisely when the collapse of the gulf occurred. It may have been as recently as within the past 10,000 years.

Today, the gulf is a canyon three-fourths of a mile long with walls reaching as high as 120 feet. A portion of the cave roof that did not collapse remains as a natural bridge that spans 200 feet and has an opening 75 feet high--making it one of the largest in the state.

Bussell Branch, which previously flowed above the intact cave system, now flows through the canyon and into a part of the cave that did not collapse. The water that flows into the cave eventually reappears at Mammoth Spring in Arkansas, seven miles away.

The gulf has long been a source of wonder to local residents and geologists alike. The first recorded exploration of the gulf was in 1884 by Maj. M.B. Norman of Alton, who owned the property, and a reporter from the West Plains Gazette. The adventurers used a boat to explore the cave and reported finding a large lake several hundred feet from the entrance.

Eight years later, Luella Agnes Owen, author and one of the first women geologists, explored the depths of the cave. Using candles to light the way, Owen boated into the lake and reported seeing "small eyeless fish, pure white and perfectly fearless; the first I had ever seen, and little beauties." Like Norman before her, Owen was prevented from going more than 500 feet into the cave because the passageway became too small.

The chance to explore the cave as Owen did was lost in 1921 when a fierce storm washed down trees and other debris into the gulf, temporarily damming the cave. Today, the cave is impassable a short distance from the entrance. After heavy rains, runoff from approximately 20 square miles drains into the gulf. This sometimes turns the gulf into a small lake, which slowly drains through the cave.