The 1862 discovery and the secret cave
John Knox was a farmer who owned the property containing the cave entrance in the early 1860s. The standard discovery story — repeated by Fantastic Caverns guides and printed in the cave's official literature — holds that Knox's dog chased an animal into a small hillside opening on the property in 1862 and refused to come out. Knox investigated, enlarged the opening, and discovered a substantial cave system extending several hundred yards into the bedrock.
Knox chose to keep the cave secret. Missouri in 1862 was deep in the Civil War — the state was officially Union but had substantial Confederate sympathies, and southwest Missouri (including Springfield) was the site of multiple Civil War battles and ongoing guerrilla warfare between Union and Confederate irregular forces. Knox feared that either side could commandeer the cave for storage, hiding personnel, or other military purposes if its existence became known. He sealed the entrance and did not disclose the cave to outsiders during his lifetime.
The cave's existence became more broadly known after Knox's death, though commercial development did not begin until much later. In 1867 — just after the war — a group of twelve Springfield-area women became the first visitors documented to tour the cave; their names are carved into a wall near the cave entrance and remain visible today as one of the cave tour's interpretive highlights. Small-scale informal tours continued through the late 19th and early 20th centuries.