Amazon warehouse workers and delivery drivers at seven facilities in the metro areas of San Francisco, Chicago, Atlanta, Southern California, and New York City are out on strike today, in what the union says is the largest strike against Amazon in U.S. history. Unionized workers at Staten Island’s JFK8 fulfillment center have also authorized a strike and could soon follow.

Workers in all these locations—five delivery stations and two fulfillment centers—have already shown majority support and demanded union recognition. The Teamsters set Amazon an ultimatum: recognize the unions and agree to bargaining by December 15, or face strikes. Amazon hasn’t moved.