NEW YORK (AP) — Amazon workers in Staten Island, New York, voted to unionize on Friday, marking the first successful U.S. organizing effort in the retail giant's history and handing an unexpected win to a nascent group that fueled the union drive.

Warehouse workers cast 2,654 votes — or about 55% — in favor of a union, giving the fledgling Amazon Labor Union enough support to pull off a victory. According to the National Labor Relations Board, which is overseeing the process, 2,131 workers — or 45% — rejected the union bid.

The 67 ballots that were challenged by either Amazon or the ALU were n...