If you live in Idaho, you know him by the name on the vanity plates of his Lincoln Town Car: Mr. Spud. But that nickname doesn't tell the whole story of a uniquely American career. J.R. Simplot may be the only man in history to become a giant in three different economic eras: agricultural, industrial, and electronic. This particular tycoon, worth an estimated $3.2 billion at the age of 93, is a walking lesson in American economic history.

As an eighth-grade dropout, he shot wild horses in the Idaho desert and used their meat to help fatten his 600 hogs. With a nest egg of $7,500 from that enterprise, he turned to farming. He fed dried potatoes to U.S. troops in World War II and, a decade later, revolutionized the fast-food industry with a process for mass-producing fries. Today he supplies more than half of all the french fries served at McDonald's. In 1980, he became the founding angel for Micron Technology, which grew into one of the leading producers of semiconductor memory in the world and one of the most-traded stocks in NYSE history.

"If it weren't for me," Simplot says by phone from his 2,200-acre home overlooking the Boise Valley, "we wouldn't have Micron. It's a biggie now. I put steam in it. I made Micron rich. We'll have most of the memory in the world when we get through. I've always had the biggest and the best, and I've led the parade."

Boise is nestled in the foothills of the Rockies, and growth—spurred largely by Simplot's entrepreneurship—has caused the city to sprawl. Millions in Simplot donations support the area's colleges, arts centers, and youth sports. Simplot himself has served on the board of trustees of Albertson College of Idaho for 63 years, which must be some kind of record. Although he's retired from Micron, he hasn't quit working for the $3 billion company that bears his name: J.R. Simplot Company.

"We're opening a plant in China," he says. "We're making french fries for McDonald's over there. Tough to find a good place to plant potatoes, but I'll find it. I was in Peking a couple months ago. They just love fries. It's true—all you have to do is go to Peking and take a look."

David Dorsey