The strike at the Pullman plant in Chicago became a nationwide strike because of the unfair treatment of laborers in the railroad industry was prevelant throughout the United States. Regardless of where citizens live, many of them were taken advantage of and paid poorly by big railroad corporations. This helped to unit them under one common cause, along this to become a national movement.
Along with this, 30 people on strike were killed by railroad operators and allies of business owners when the strike began. This incited fury throughout the railroad community. So all over the country, other laborers went on strike as a means of solidatarity for those who were killed in the initial strike.