Sinclair Broadcast Group, SBGI -3.73% Inc., the owner of the most local TV stations in the country, has purchased and next spring will relaunch the defunct mobile news site Circa, the company announced Monday.

Sinclair has hired John Solomon, formerly the vice president for content and business development for The Washington Times, to lead the effort as chief creative officer. Mr. Solomon said he plans to hire 70 journalists to do original reporting, in addition to having access to video feeds from the 172 television stations that Sinclair owns and runs.

Circa was founded in 2011 as a way of making news more easily digestible on mobile devices. It became particularly well known for its feature that let users sign up to receive rolling updates on breaking stories via push notification. Matt Galligan, the site’s founder, wrote in June that the site shut down after failing to close a needed round of funding. It had raised nearly $6 million.

Photo: Associated Press

Rob Weisbord, the vice president and chief operating officer of Sinclair’s Digital Group, said Sinclair’s digital arm had been in talks with Circa before it ran into financial troubles, drawn to its technology and independent brand. Sinclair bought Circa’s technology and intellectual property for $800,000 in March, the company said.

“We were intrigued by their mobile app tech stack with a ‘follow me’ feature that allowed content personalization by the end user,” he said in an interview. Circa will run as its own independent company.

Sinclair wanted to invest in the millennial-focused site because the audience for local TV news is aging, he said, in part because local TV stations have not been good at finding young audiences where they are – on mobile devices and over-the-top streaming players like Roku and Xbox. Mr. Weisbord said he hopes to put Circa on these platforms in the future.

The newly relaunched and redesigned Circa will be focused on original reporting, user-generated content and letting readers make up their own minds about stories. It will also feature the kind of irreverent tone that does well among young audiences on social media, Mr. Solomon said.

“If we can bring context, analysis and depth – and a little bit of humor—I think we can create something special in the marketplace,” he said. “So much of what’s happened in the marketplace has been partisan-driven.”

Mr. Weisbord said the left-leaning nature of the most popular news sites for young people left an opening in the market.

“The key is to be independent and user-generated, because when you look at the Vices and Voxes of the world, they tend to be far-left,” he said. “Our goal is to let the content drive it. It will never be far right like where Breitbart is, because our research shows there is no way to gain a big audience if we do that. But there’s a big need in the center.”

Sinclair Broadcast Group famously caused controversy in 2004 by announcing plans for a prime-time airing of a documentary critical of then-presidential candidate Sen. John Kerry’s Vietnam war record, just ahead of the election. After a furor, the company ended up airing only parts of the documentary in a news program.

Under Sinclair, company executives say, Circa will be a bit more open-minded about its business model than in its previous iteration, in which it focused on so-called “native ads” and shunned off-the-shelf advertising formats. Mr. Solomon and Mr. Weisbord said native ads, documentary sponsorships and more traditional ad formats like pre-roll video advertising will all likely have a role to play, but the initial focus is to attract an audience. Circa’s first year operating budget will be “just under $10 million,” the company said.

Long term, Mr. Weisbord hopes to use Circa’s intellectual property in Europe to expand the digital brand internationally, he said.

“We expect it to be as significant as Vice and Vox and Buzzfeed,” he said. “They all went to broadcasting companies for investments. They want to expand into broadcasting. They started out as pure-play (digital) and they are now entering into our field. We are going the other way.”

Write to Keach Hagey at keach.hagey@wsj.com