Following the Great Merger of 1911, Pacific Electric divested most of its Los Angeles local routes to LARy, allowing D to use former Los Angeles Inter-Urban Electric Railway trackage on West 6th street Westlake.

[2] The Figueroa and 7th street portions of the line were eliminated, shortening the trip by one-quarter mile (0.40 km).

In 1921, the Bonnie Brae Line was given the letter designation D.[3][4] Cars originated at Fifth and Central, running west via Fifth; Olive; Sixth; a private right of way; and Larchmont as far as Melrose.

Ridership along the route spiked in World War II, necessitating extending the service down U line tracks to Slauson.

[8] The route was removed by Los Angeles Transit Lines in 1947, largely replaced with trolley coach service.