The route's origins begin when the streetcar lines running on Washington Street and Maple Avenue were combined into a single service in 1912, running through
Downtown. During the 1920 rerouting, the Washington Street line was spun into the
West Washington and Garvanza Line.[2] Thus, the Maple and Heliotrope line consisted of tracks on Melrose; Heliotrope; Temple; New Hampshire; First; Bimini Place; a private right of way; 2nd; Rampart; 6th; Alvarado; 7th; Maple; Woodlawn; Santa Barbara; Wall; and 53rd.[3] The Maple segment became the south end of the new line, which ran to Melrose to Normandie in
Melrose Hill. The line was given the letter designation H in 1921.[4][5] Service between First and the University of California was temporarily discontinued in the summer of 1924 amid citywide power cuts.[6] The western end was rerouted via Vermont and Beverly in 1924 and extended to Melrose and Western the following year. This routing pattern held until August 3, 1947 when service was discontinued.[2][7]
^"May 1: This Date in Los Angeles Transportation History". Metro Dorothy Peyton Gray Transportation Library and Archive. Los Angeles County Metropolitan Transportation Authority. Retrieved February 16, 2022. 1921: Large letter signs indicating the routes of different lines are placed on top of Los Angeles Railway streetcars.
^"Cars To Have Letter Signs"(PDF). Two Bells. Vol. 1, no. 48. Los Angeles Railway. May 2, 1921. p. 1. Retrieved February 16, 2022.