Editor’s Note: Vote for your top pick among Inc.'s 35 Under 35 Coolest Entrepreneurs of 2014. Inc.com announces the Readers' Choice winner Thursday, June 26.

Chad Halvorson thought he had it pretty good as far as high school jobs go in the blustery small town of Thief River Falls, Minnesota; he was a bag boy at the local grocery store. One detail irked him, though: having to stop by the store on his days off to check the schedule and, sometimes, request to change shifts.

In 1998, he plunked down $100 of his hard-earned cash to do something about that fact (it was also something that baffled his parents): He registered the Internet domain WhenIWork.com. His vision for it at that point was exceedingly simple: a website where managers could post calendars of workers' schedules, and where hourly employees--a whopping 60 percent of all humans employed in the United States--could find their shifts.

"The hourly work force is a forgotten world," Halvorson says. "When you look for business apps, they're all for people who work salaried jobs or in corporate offices. There's a lot--a lot--we can do to help make life easier for everyone else."

He built the site in 2000, but in pitching it to a variety of mall-shop-type businesses, it became clear that the idea was interesting but not entirely useful: Most hourly workers at that point didn't have reliable, regular home Internet connections.

"I put it on the shelf and started a consulting company instead," Halvorson, 31, says. He became an actual pro at building websites during college, and his bootstrapped company, ThisClicks.com, put Halvorson through college and eventually employed a few other people over the next 10 years in St. Paul.

During that decade, the cultural and technological scaffolding that When I Work needed to function at scale was built up around it: Now, even rural workers had high-speed Internet and smartphones. Luckily for Halvorson, he was still holding on to not just the concept behind When I Work but also the Web domain. He, along with part of his team at ThisClicks, including CTO Dan Olfelt, got to work building a When I Work app on the side.

After a year of in-house development, the app launched in 2010, with a 30-day free trial for employers. "When we launched it, we didn't even have a mechanism in place to charge people money," Halvorson says. "We thought, We don't have to bill people after the 30-day free trial."

The first paying customer ($19 a month) came 45 days later, and dozens more--not just restaurants and retail stores you'd expect, but also hospitals, fire departments, and water parks--were signing on weekly. Halvorson says managers tell him they used to spend up to 20 hours a week scheduling employees. But with the use of When I Work, they now spend an average of 30 minutes a week.

When I Work has more than 4,000 customers from the employer side, and more than 200,000 people use it regularly. This hyperfast growth attracted local venture capitalists and also caught the eye of Tom Gieselmann, a co-founder and general partner of E.ventures, a venture capital firm in San Francisco.

"We identified When I Work thorugh our data-mining efforts," Gieselmann says. (His firm tracks data from Alexa, iTunes, Quantcast, and Google Trends, using Crunchbase's API.) "It showed off a very promising growth spurt."

Gieselmann admits that many of the companies brought to his attention strictly by their numbers don't pan out as good investment opportunities, but in the case of When I Work, after a short phone call with Halvorson, he hopped on a plane to Minnesota. He says he found Halvorson a highly capable CEO who had built a company even more promising than the data might suggest.

"He really cares about the team, and he wants to build a very supportive culture," Gieselmann says. "He is insanely open to feedback, because he knows he doesn't have all of the answers. But he is not afraid of making decisions."

When I Work is in a growth spurt now, thanks to an infusion of $4 million from E.ventures, Arthur Ventures, and Greycroft earlier this year. When I Work, which has split off from its parent, ThisClicks, is moving to an airy new office in St. Paul, and it's hiring.

"In our space, people don't always move fast," Olfelt says. He means the company's schedule-management competitors that offer a couple of legacy systems, including Kronos, and the middle manager's crusty default spreadsheet, Microsoft Excel. There's one direct competitor aiming squarely at the When I Work small-business market, the Austin startup Hot Schedules, which was co-founded by a former P.F. Chang's bartender and his manager. The fresh funding gives When I Work a shot in the arm--and an opportunity to think beyond scheduling shifts for feeding penguins at the Columbus Zoo or selling concessions at Atlanta Braves games.

"We are going to look at what we can do and the companies we can work with from a talent-management and training aspect, too," Olfelt says. "We could transform the way they work and interact with technology and their work."