When Mr. Hendricks went to a Janesville bank to finance the purchase of the plant, he was turned away. “The banker said, ‘We don’t do business with entrepreneurs, and we don’t want your business,’” Ms. Hendricks recalls.

It was a turning point. The couple turned their backs on Janesville, focusing instead on Beloit.

They would move from renting local apartments to starting ABC Supply in 1982, buying up distributors nationwide.

Beloit at the time was on the cusp of a steep decline after successive economic blows, among them the grinding to a halt of Fairbanks Morse, a diesel engine maker and a onetime major employer.

Like struggling cities and towns across the country, Beloit went through a period of Band-Aid-like efforts. By the 1980s, local businesses were petitioning the city to change its image by cleaning up the riverfront, where vacant stores sat along the banks of the river, and by reviving the withering downtown. The initiatives barely made a dent.

Into the 1990s, at least, the town still had its foundry, Beloit Corporation, by that time owned by a Milwaukee company, Harnishfeger Corporation. At its height, Beloit Corporation had employed more than 7,000 people building papermaking machines. Late into the night, the flickering light from the welding in the foundry would light up the Rock River.

In 1999, the foundry went bankrupt, leaving behind an empty, sprawling complex the size of 15 football fields. Beloit’s downtown became a bleak landscape of “decayed, bombed-out buildings,” recalled Jeff Adams, who moved to Beloit to teach economics at Beloit College in the early 1980s and was involved in early initiatives to try to fix the town.

But if Beloit was sinking, the Hendrickses were riding high. Their business was booming, and they saw opportunity in the desolation.