Almost one year ago, Brockton resident Felicita Sepulveda made a call to JetBlue asking for a last-minute ticket to Puerto Rico. Just four days after Hurricane Maria struck her family’s homeland, Sepulveda was frantically heading home to search for her brother, who had been missing since the start of the storm.

Labor Day morning, approximately 300 people gathered on Boston Common to march in support of strong labor unions and a $15 minimum wage, according to an official Facebook page for the rally. Organizers...