The street railways began replacing horse car lines after electric motor technology was perfected in the late 1800s. Ridership boomed almost overnight and led to the commuter lifestyle. Rails extended beyond the city limits, allowing the development of suburbs.
The trolleys expanded their warm weather business by building amusement parks on their lines. Before cars were available to the general public, people took trolley excursions to the parks like New York's Coney Island.
Over 100,000 people were employed by the street rail industry by the time of World War I, making it the fifth largest industry in the States. As cars and buses became plentiful, however, the trolleys saw their business decline. World War II brought a reprieve for those lines still in business. Americans again turned to public transportation with the rationing of tires and gas, and the unavailability of new cars as factories switched to war production.
The war ended and with it, the trolley's new life. New cars were once again available, and folks wanted the freedom to travel when and where they desired, unrestricted by the trolley schedules.