This balance did not come about accidentally. Natural foods companies like Wild Oats Markets and Celestial Seasonings started here, and several national labs and big-tech companies like I.B.M. opened outposts. Early on, the biotech, telecom and data storage industries took off in Boulder, bolstered by Sun Microsystems’s $4.1 billion acquisition of Storage Technology in 2005.

“That generation of entrepreneurs had their success, and importantly, they don’t leave,” said Brad Bernthal, director of the entrepreneurship initiative at the University of Colorado Silicon Flatirons Center. “Lots of places, you get your money and you go retire somewhere. This place is a destination for people.”

The center makes sure that those veterans cross paths with young entrepreneurs. It hosts meet-ups, a campuswide business plan competition and a law clinic, where entrepreneurs get free legal help on things like intellectual property protection.

TechStars, a three-month mentorship program that has taken place in an old gym in Boulder since 2007, has spurred the start-up community’s growth. Of the first 10 companies that went through the program, eight received venture funding, five were acquired by bigger companies and three are still active. But David Cohen, the founder of TechStars, is equally proud of one of its failures, because he said it showed how supportive Boulder’s tech community is. After EventVue, which built online communities for conferences, shut down, job offers from other tech companies came pouring in.

Almost half of the 30 companies that have gone through the TechStars program have decided to stay in town. Several of them share space — tiny offices and a big common room, kitchen and deck — above Aji, a Latin American restaurant downtown.

Image Technology entrepreneurs meet at a twice-a-month coffee club. Credit... Kevin Moloney for The New York Times

One is Everlater, for making travel journals on the Web. Its founders, Nate Abbott and Natty Zola, moved to Boulder to save money by living in their parents’ basements after quitting their jobs on Wall Street. But when they arrived, Mr. Zola said, “We realized it was an incredible place to start a company.”