The sprawling 150,000-square-foot new headquarters of Clam Outdoors off busy I-94 in Rogers is light years away from Dave Genz's garage, where he started hand-making "Fish Trap" portable ice shelters nearly 35 years ago.

"My wife, Patsy, sewed them on her machine,'' said Genz, 67, of St. Cloud, whose invention is credited with revolutionizing ice fishing. "We made five that first year, then 20 the next and 80 the third year.''

Nowadays Clam Outdoors sells tens of thousands of portable ice fishing shelters yearly — more than anyone else — as well as accessories ranging from rods and lures to clothing and bait buckets.

"It's the American dream — we started in our garage and now it's the No. 1-selling fish house in the world,'' Genz said. "I never dreamed it would get as big as it has.''

Genz sold the licensing rights to Clam in 1992 but has continued to work for the company as a promoter, ambassador and adviser, attending sports shows, giving seminars and doing TV and radio shows.

"Dave's responsible for what ice fishing is today,'' said Nick Chiodo, Clam's director of marketing. "Every house out there on a sled is a version of what he started in his garage. It's incredible. He is Mr. Ice Fishing.''

But Genz acknowledged he couldn't have taken the company to where it is today — a leader in the industry and one diversifying beyond ice fishing, too. Dave Osborne, 56, of Wayzata, bought Clam in 2003 and has overseen its remarkable growth. When he bought it, Clam sold about eight products.

"Now we have more than 750,'' he said, including the popular IceArmor clothing. "I always say it's better to be lucky than good. When I jumped in, I didn't know it [ice fishing] would take off like it has. He [Genz] started it, and we've brought it mainstream.'' Clam has had double-digit sales growth nearly every year since Osborne bought it.

Osborne, who grew up in Cyrstal, also owns a national commercial fixture installation company based in Plymouth. He bought Clam after a casual conversation with a neighbor who worked there. "It seemed like it had some possibilities,'' he said.

It clearly did.

"My motto is I would rather try and fail than not try to do it at all,'' Osborne said. "Without risk there is no reward.''

Ice fishing revolution

Genz's early houses were made from cotton canvas, metal electrical conduit piping and wood — crude by today's standards, but effective. "I sawed the conduit with a hacksaw,'' he said, and he enlisted help to assemble the houses. "My friends, relatives and neighbors would help.''

The portable shanties gave anglers shelter from the cold and wind but, more important, gave them mobility on the ice so they could move and locate fish.

Today, the shelters are lighter, more comfortable and have more features. Clam offers about two dozen types, including some made from thermal insulated material, keeping anglers warmer and reducing condensation. "Hub shelters'' — collapsible, tent-like shelters with room for up to seven anglers — offer another dimension for group fishing.

Electronics, power augers, warmer clothing and portable fish houses all have helped entice people onto frozen lakes.

"We make it fun to go outside in the winter,'' Genz said. "We're Minnesotans; we should enjoy winter.''

Another reason for ice fishing's popularity — no one really knows how many of Minnesota's 1 million angers fish through ice — is that it is cheaper than open-water fishing. You don't need a $40,000 boat, motor and trailer.

"Ice is the greatest equalizer when it comes to allowing someone to get out and fish,'' Chiodo said.

The two-person, top-selling Clam Nanook costs $400. Add an electronic fish finder, rod and lures, and for less than $1,000 you're in business.

"You don't have to take out a second mortgage,'' Chiodo said.

Ice fishing evolution

The sport continues to evolve. Because ice fishing is more comfortable, more kids and women are getting on the ice, Chiodo said. Still, males age 25 to 57 dominate the market.

But even in fish-frenzied Minnesota and with a burgeoning product line, Osborne said his company needed to expand outside of ice fishing to garner year-round business for his 27 employees.

In 2005, Clam bought Polar Sports, which makes utility trailers and accessories for ATVs and lawn tractors. And Clam began making free-standing screened shelters for back yards or cabins in 2012.

"They go up in 45 seconds,'' Chiodo said. The company used the same technology to produce a collapsible camouflage thermal hunting blind.

"We try to do things unique that no one else is doing,'' Osborne said.

Currently about 80 percent of his business remains linked to ice fishing, but he's hoping to further diversify.

Meanwhile, Genz is busier than ever, fishing and promoting the sport at seminars and on TV and radio. Twenty-seven years after quitting his job as a maintenance engineer to go into the fishing business full-time, retirement isn't in the cards.

"I'm not doing anything I care to retire from,'' he said. He recently tied into a mess of 12½-inch crappies.

"The evening bite was phenomenal. It was nonstop catching,'' Genz said. "It doesn't get old.''

Doug Smith • doug.smith@startribune.com

Twitter: @dougsmithstrib