• Amazon workers at a Staten Island warehouse voted Friday to join a union, the first time that's happened at one of the company's U.S. facilities.
• The outcome represents a landmark win for organized labor, which has for years tried to organize Amazon warehouse and delivery workers.
• By voting in a union, Staten Island workers stand to disrupt Amazon's current labor model, which is the backbone of its Prime two-day shipping promise.

Employees at an Amazon warehouse on New York's Staten Island voted Friday to join a union, a groundbreaking move for organized labor and a stinging defeat for the e-commerce giant, which has aggressively fought unionization efforts at the company.

The tally was 2,654 votes in favor of joining the union and 2,131 opposed. Approximately 8,325 workers were eligible to vote whether to become part of the Amazon Labor Union. There were 67 challenged ballots, a gap that's too narrow to change the outcome of the election. The results still need to be formally certified by the National Labor Relations Board.

The Staten Island facility, known as JFK8, is Amazon's largest in New York and now has the distinction of being the first in the U.S. to unionize despite workers having to stare down a hefty anti-union campaign. Amazon papered the walls at JFK8 with banners that proclaimed "Vote No," set up a website and held weekly mandatory meetings. It even hired an influential consulting and polling firm with close ties to Democratic political groups, and touted its own benefits over those offered by unions.

By voting in the Amazon Labor Union, Staten Island workers could challenge the company's current labor model, which is the backbone of its Prime two-day shipping promise. Unions stand to disrupt the level of control that Amazon exerts over its warehouse and delivery employees, like its ability to unilaterally set the pace of work and hourly wages, labor experts previously told CNBC.

"We're disappointed with the outcome of the election in Staten Island because we believe having a direct relationship with the company is best for our employees," an Amazon spokesperson said. "We're evaluating our options, including filing objections based on the inappropriate and undue influence by the NLRB that we and others (including the National Retail Federation and U.S. Chamber of Commerce) witnessed in this election."

The ALU has called for Amazon to put in place "more reasonable" productivity rates in the warehouse. It's also urging the company to raise wages, as well as give workers more paid breaks and vacation, among other demands.

The ALU was an unlikely contender to win the first unionized Amazon warehouse. Started in 2021, it's a grassroots, worker-led organization that's largely depended on crowdsourced donations from a GoFundMe account to fund organizing activities.

The union is led by Christian Smalls, a former JFK8 manager, who was fired by Amazon in 2020 after the company claimed he violated social distancing rules. Smalls argued he was fired in retaliation for staging a protest in the early weeks of the coronavirus pandemic to call for stronger safety measures.

Smalls quickly became a leader of worker activism at Amazon and elsewhere. He spoke out at rallies criticizing Amazon's labor record, and at one memorable protest, set up a guillotine outside Amazon founder Jeff Bezos' Washington, D.C., mansion to call for higher wages.

Amazon executives took notice of Smalls' activism. A leaked memo obtained by Vice revealed David Zapolsky, Amazon's general counsel, had referred to Smalls as "not smart or articulate" in a meeting with the company's top executives, an incident that further angered critics of Amazon's labor practices.

Amazon still faces another labor battle at its Bessemer, Alabama, warehouse. The NLRB called for a do-over election last November after it determined Amazon improperly interfered in the first election, which was held last spring.

Worker activism inside Amazon has surged since the Covid pandemic hit the U.S. in early 2020. Before the first election in Bessemer, the last substantial union vote at a U.S. Amazon facility took place at a Delaware warehouse in 2014, when a group of repair technicians voted 21 to 6 against joining the International Association of Machinists and Aerospace Workers.

The vote tally in Bessemer wrapped up Thursday, but the outcome is still too close to call. There were 993 votes opposing the union and 875 in favor. The outcome hinges on some 416 ballots that remain challenged by Amazon and the Retail, Wholesale and Department Store Union. The NLRB will set a hearing in the coming weeks to determine whether the ballots will be opened and counted.

WATCH: Amazon workers in Alabama vote down unionization