Sam McBride, Jared Smith, Peter Rahal and Jessie Stewart, all of whom grew up in Glen Ellyn, started the company with the idea to make healthy power bars.
Co-founders Rahal, 31, and Smith each put in $5,000 in spring 2013 to launch the company in a small kitchen, according to the company website.
The bars are made with egg whites, fruits and nuts, and exclude dairy, soy or gluten.
The original four employees have a long history together as they all attended Hadley Junior High and Ben Franklin Elementary School before graduating from Glenbard West in 2004.
The company started small, selling to health clubs and people who wanted a healthy diet. In 2014, Chicago Bar Co., the parent company's name, grew and they were soon shipping by the truckload. According to the company website, they learned through trial and error.
They launched new packaging and landed their first grocery distribution deal with Wegman's. "And then the floodgates opened. It's been a rocket ship," according to the site. The protein bars gained popularity after editors at Women's Health and People magazines raved about the product.
The founders will continue leading the company after the deal is complete, most likely by the end of the year.
The purchase comes just days after Kellogg hired a former Nature's Bountyvitamin executive Steven Cahillane as its CEO.
The Battle Creek, Michigan-based company -- best known for Frosted Flakes and Pop-Tarts -- has struggled to make its cereals and snacks more appealing to Americans who want to avoid sugary processed foods. The company brought in Cahillane as it seeks to offer healthier packaged foods.
• The Associated Press and Daily Herald Business Writer Kim Mikus contributed to this report.