They were handing out free chocolate cupcakes to anyone who registered to vote on Monday near Pier 39 in San Francisco, but that’s not why Christine Libbey signed up.

“After what happened in 2016, a lot of people like me woke up,” she said. “I’m taking this thing a lot more seriously now.”

Libbey, a 25-year-old doctoral psychology student at Alliant International University on Beach Street, stopped by the front desk of the school library and picked up the registration form. And the cupcake.

I understand what’s at stake,” she said. “I let it go last time. I’m trying to be hopeful about the future.”

Libbey, who said she sat out the 2016 election but won’t miss the next one, was one of tens of thousands of new voters estimated to have stopped by the more than 4,000 voter registration displays set up across the U.S. as part of the annual National Voter Registration Day.

The cupcakes were the idea of Alliant librarian Dean Jones, who called it his civic duty to get students involved and to the polls, even if that meant paying for three dozen cupcakes out of his own pocket. That’s the going cost of encouraging democracy this week.

“It’s not a big deal,” Jones said. “But you don’t get a cupcake unless you register. If I gave a cupcake to everybody, we’d run out.”

National Voter Registration Day, which happens every fourth Tuesday in September, usually is forgotten by every fourth Wednesday in September. Not this year, organizers said, even if the goal has always been about participation over party preference.

“We’re not partisan; we believe that this one single day can raise awareness for everyone,” said Brian Miller, director of National Voter Registration Day, a Virginia-based nonprofit foundation. “We believe democracy works best when more people vote.”

Every year, Miller said, millions of Americans fail to cast a ballot because they missed a registration deadline, failed to update their registration or aren’t sure how to register. On Tuesday, volunteers staffed booths, rang doorbells, dialed phone numbers and walked the streets to make sure no one had any excuse come the first Tuesday after the first Monday in November.

In 2016, Miller said, about 750,000 voters used National Voter Registration Day to get qualified to vote across all 50 states. In the Bay Area, voter registration events were also held at AT&T Park, at libraries in South San Francisco, Millbrae, Alameda and San Bruno, and at the Sharp Park Golf Course clubhouse in Pacifica, where golfers are always seeking to correct mistakes.

Steve Rubenstein is a San Francisco Chronicle staff writer. Email: srubenstein@sfchronicle.com Twitter: @SteveRubeSF