Read the excerpt from We Shall Not Be Moved.

Yet what they wanted was modest enough: a fifty-two-hour week with extra pay for overtime, an end to the fines and petty tyrannies, and a living wage. These were the demands that were hammered out by the shop groups behind the closed doors of the meeting halls. The officers of Local 25 sent them on to the owners — along with one more demand, recognition of the union.

Which historical detail best helps clarify a reader’s understanding of the information in the excerpt?