Postmaster Harlow tested the new service in 1891. The first service began the next year. Brooklyn, NY followed, inaugurating its service in 1894.
Mail trolley cars were painted white to stand out. In some cities, street collection boxes at some intersections were also painted white – designating them for use in conjunction with the trolleys.
By the end of 1895 Boston, Chicago, Cincinnati, New York, Philadelphia and Washington, D.C. were using mail trolleys. Seventy-five clerks worked on mail trolley cars, handling more than 500,000 pieces of mail a day.