Labor and union tensions intensified in wartime America, as workers fought for higher pay and safer conditions and companies fought the influence of unions. In December 1917, tension between the Twin City Rapid Transit Company and its streetcar workers hit a high point as the TCRTC company owner refused to meet employees' demands and rewarded "loyal" nonunion workers. A peaceful demonstration in St. Paul turned violent as a mob attacked streetcars and nonunion workers. The Minnesota Home Guard was called in to restore order; this photo was taken at that demonstration.

A streetcar workers' strike took place later that month. The federal government recommended that the TCRTC rehire the union workers it had fired, but the TCRTC refused. Eight hundred union streetcar workers lost their jobs and were replaced by nonunion workers.