Starbucks workers have expanded their strike to more cities and closed 59 stores across the U.S. as of Monday, the union said amid stalled negotiations.

Workers in about 10 to 15 stores across the Los Angeles, Seattle and Chicago areas kicked off the strike, which spread to a similar number of stores in three additional metropolitan areas each day. By Monday, baristas in more than 50 stores in cities like Boston, Dallas, Denver, New York and Philadelphia did not report for work.