Raymond N. Plank, a World War II bomber pilot who watched from the air as a mushroom cloud formed over Nagasaki, then returned to the United States to build Apache Corp. into one of the country’s largest independent oil and gas companies, died Thursday at his home in Ucross, Wyoming. He was 96.

Plank suffered a fall last year and was in declining health, said his son Roger Plank.

The son of a Twin Cities corn farmer, Plank knew next to nothing about oil and gas when he founded Apache with two friends and $250,000 of seed money in 1954. But he went on to become a dominant figure in an industry known for its iconoclastic characters – a cigar-smoking executive who shot prairie dogs while driving through Wyoming in his Jeep, devised innovative investment vehicles from his offices in Denver and Houston, and traveled the world to monitor drilling sites from the Egyptian desert to the North Sea.

Apache found a niche by buying up smaller concerns and beefing up their operations, while scouting untapped fields. an Gordon’s opera “The Grapes of Wrath” were partly created at the ranch.