Mark Zuckerberg has been an evangelist for the power of social networks for years. Now he wants his network, Facebook Inc., to fill the role that churches and social clubs once did in communities.

Speaking in Chicago last week, the Facebook FB, +2.12% co-founder and chief executive said that Americans are more disconnected from their communities these days, and need something to unify them.

“It’s so striking that for decades, membership in all kinds of groups has declined as much as one-quarter,” he said. “That’s a lot of people who now need to find a sense of purpose and support somewhere else.”

Zuckerberg said he thinks Facebook can fill that role in organizing communities.

“ ‘If we can do this, it will not only turn around the whole decline in community membership we’ve seen for decades, it will start to strengthen our social fabric and bring the world closer together.’ ” — Mark Zuckerberg

“We all get meaning from our communities. Whether they’re churches, sports teams or neighborhood groups, they give us the strength to expand our horizons and care about broader issues. Studies have proven the more connected we are, the happier we feel and the healthier we are,” he said.

“People who go to church are more likely to volunteer and give to charity — not just because they’re religious, but because they’re part of a community.”

Zuckerberg is in the middle of a yearlong effort to visit every state, and meet the people who use his network.

Of course, Zuckerberg’s comments weren’t entirely altruistic. He also said he’s hoping to significantly boost the number of users of Facebook’s artificial-intelligence-powered “communities” feature. While Facebook has 2 billion users worldwide, only about 100 million are part of “meaningful communities,” he said. Zuckerberg said he hopes to get 1 billion users to join Facebook communities.

“We’re going to change Facebook’s whole mission to take this on,” he said.