Born in Caddo, Texas, in 1919, Steen was the son of Charles Augustus and Rose Steen. He attended high school in Houston and went on to study at John Tarleton Agricultural College in Stepenville. In 1940 he transferred to Texas College of Mines and Metallurgy at El Paso, where he received a B.A. degree in geology in 1943.

Following graduation, Steen discovered that, due to poor eyesight, he was ineligible for the draft during World War II. Consequently, he worked as a geologist in Bolivia and Peru through 1944 and 1945. Upon returning to Texas, he married Minnie Lee ("M.L.") Holland, a graduate of Hardin Simmons University.

Steen completed one year in graduate school at the University of Chicago and then returned to Houston to accept a job doing field work for the Standard Oil Company of Indiana. After two years, he was fired for insubordination and blacklisted as a geologist throughout the entire oil industry.

In 1949 Steen read an article in the December issue of The Engineering and Mining Journal announcing that the federal government had issued a call for prospectors to locate a domestic supply of uranium. Despite the fact that his sons John, Charles, Jr., and Andrew were all under four years of age and M.L. was expecting their fourth son, Mark, he accepted a $1,000 grubstake from his mother and headed for the Colorado Plateau.

Most uranium prospectors used a Geiger counter to detect radiation. Steen could not afford such an instrument and instead used a secondhand diamond drill rig to supplement his geologic training in his search. Eschewing standard uranium-hunting methods, he had an original theory that uranium would collect in anticlinal structures in the same manner as did oil. Others on the Colorado Plateau joked about "Steen's Folly."

When Steen's son Mark was born, his family joined him in a small house trailer at Dove Creek, Colorado, later moving to a tarpaper shack near Cisco, Utah. Finally, on 6 July 1952, after two years of tramping the desert and feeding his family poached venison and cereal, Steen hit pay dirt in the Big Indian Wash of Lisbon Valley southeast of Moab. His Mi Vida mine was the first big strike of the uranium boom and proved that there was a generous supply of uranium on the Colorado Plateau.

Stories of Steen, the "Uranium King," are legion. In Moab he built a $250,000 hilltop mansion with swimming pool, a greenhouse, and servants' quarters. He formed Utex Exploration Company, Moab Drilling Company, Mi Vida Company, Big Indian Mines, Inc., and (later) the Uranium Reduction Company, and invited the entire population of Moab to annual parties in the local airport hangar. He had the work boots he had worn prospecting bronzed and flew to Salt Lake City in his private plane for weekly rhumba lessons. He also donated $50,000 toward a new Moab hospital and contributed land for schools and churches.

In 1958 Steen was elected to the Utah State Senate. But disillusioned by high taxes and the defeat of his attempts to introduce legislation for Utahns to purchase liquor by the drink, he resigned from office in 1961 and moved to a ranch south of Reno, Nevada. There he built a 27,000-square-foot mansion next to the fabled palace of the Comstock millionaire miner, Sandy Bowers.

Steen and his partners sold Utex and the Uranium Reduction Company to Floyd Odlum's Atlas Corporation in 1962. Steen began diversifying his interests by investing in such ventures as Arabian horse breeding, a marble quarry, an executive prop-airplane factory, a pickle plant, and real estate. He was plagued by losses and misfortune. In 1968 he was thrown into bankruptcy after the Internal Revenue Service seized his property for back taxes he owed, and in 1971 he suffered a severe head injury while operating a coring drill at a copper prospect. Steen and his wife now reside in Longmont, Colorado, where he and son Mark are developing the old Cash Gold Mine, his only remaining legacy from the uranium boom.