MILWAUKEE - Ken Hendricks, a high-school dropout who became a self-made billionaire and a driving force in the redevelopment of Beloit, Wis., died early Friday after falling through a hole in the floor of an addition being built at his Rock County home.

Hendricks, the 66-year-old founder of ABC Supply Co. Inc. in Beloit, suffered massive head injuries and died in surgery at a hospital in Rockford.

The accident happened about 10 p.m. Thursday. Hendricks and his wife, Diane, had just returned home and Ken Hendricks walked out to inspect the progress of the construction work, Rock County Sheriff's Department Commander Troy Knudson said.

"There were blue tarps that were covering open areas that were nailed in place by two by fours and it appears he fell through one of those tarps," Knudson said.

Hendricks fell more than 10 feet to the basement and struck his head, authorities said. No underlying medical condition figured in the accident, said Sue Fiduccia, Winnebago County, Ill., coroner.

Hendricks' death shocked and saddened many in Beloit, where he has been a key benefactor - bringing in companies, creating jobs, fostering the arts and restoring abandoned industrial buildings.

"His impact is phenomenal," Beloit assessor Dan McHugh said. "It really cannot be (overstated) what he has brought to this city in terms of development, especially redevelopment. Most communities of our size, their older manufacturing buildings are either being torn down or left vacant, whereas ours are the pride of the city."

That's almost entirely Hendricks' doing. Over the last 15 years, he has revived two huge, abandoned factory complexes in the heart of Beloit and spearheaded a host of other development efforts. So extensive are his real estate holdings that they make up 3.3 percent of the city's total property value.

"It's almost a matter of what hasn't he done," said Ron Nief, public affairs director at Beloit College and a friend of Hendricks. "I think probably the most important thing he's done for Beloit is inspire."

Hendricks grew up in Janesville, Wis., but he took Beloit as something of an adopted home, helping it battle deindustrialization and a negative image.

"He looked on Beloit as a great fixer-upper, and he's devoted his life to that," Nief said.

From Beloit, Hendricks built ABC Supply into a nationwide distributor of roofing, siding, windows and other building products. The company now has 390 locations, 6,000 employees and nearly $3 billion in annual sales.

Hendricks estimated a year ago that besides ABC he owns 30 other firms with combined sales of $1.5 billion. Forbes magazine recently estimated his net worth at $3.5 billion, making him the 91st-richest American.

Wisconsin has at least nine billionaires by Forbes' count, and Hendricks ranks third among them, behind John Menard Jr. and Herbert Kohler.

But with his lack of formal education, his self-made status and his impact on Beloit, Hendricks is probably the state's most unusual billionaire. Just last December Inc. magazine put him on its cover - smiling broadly, shirt open at the collar, no tie - as its national entrepreneur of the year.

Hendricks clearly was proud of his accomplishments, particularly his rise from humble beginnings - his father was a roofer - and over adverse circumstances.

But he also was something of the rich guy next door. He played country music on the radio in his Jeep. One of his favorite dining spots was Skip's Friendly Village, an unpretentious bar/restaurant known for its "Stump Burgers." And he loved going to the dump.

"He'd go to the junk yard and come back with more than he threw out," Jack DeMunnik, a friend and employee said. "Apparently Diane made him take the trailer hitch off his car."

Or so the story went, but there's no doubt Hendricks hated waste of any kind. And his passion for retrieving old factory buildings from the scrap heap is clear to anyone visiting the center of Beloit.

ABC's headquarters occupies what once was the abandoned, run-down Fairbanks-Morse complex. Downtown, Hendricks bought 35 acres filled with the buildings of the defunct Beloit Corp. and installed a variety of new businesses and sleek offices.

Also there is a museum featuring sculpture fashioned from old papermaking machinery patterns. Tens - maybe hundreds - of thousands of the patterns had been left in storage and were about to be thrown away by the previous owners. Hendricks, aghast, paid $35,000 for the lot and got DeMunnik to start turning them into art.

Hendricks has had his critics, particularly when he owned a large number of rental homes in Beloit in the 1970s. But for the last 20 years or so, it's been pretty much local-hero status.

"It's kind of unusual to have a champion of the stature of a Ken Hendricks," Beloit city manager Larry N. Arft said. "Communities do have their leading citizens who support philanthropy and the arts . . . but this was kind of an extraordinary relationship."

Hendicks dropped out of high school at 17 when he became a husband and father. Working two full-time jobs, he started roofing on the side.

By age 30 he had 500 roofers working for him and was handling jobs at military bases and large stores. In 1982, he and Diane, his second wife, started ABC Supply. Among the other firms in which Hendricks owned controlling interest are several he either brought to Beloit or got started there.

The effect of Hendricks' death on ABC won't be clear for some time. He held the positions of chairman and CEO. David Luck, a former Bridgestone/Firestone executive, has been ABC's president and chief operating officer since 1998.

Diane Hendricks is the firm's executive vice president and plays an active role in management, as well as in philanthropic activities in and around Beloit.

Five of the Hendricks' seven children also work at ABC.

(c) 2007, Milwaukee Journal Sentinel. Distributed by McClatchy-Tribune Information Services.