The B line ran out Brooklyn Ave. and City Terrace Ave. to Miller. In the other direction it ran out 12th St. to Hooper and ended up at Ascot & 53rd St.
Here we have a 1920s view of a streetcar northbound on North Main Street passing the Plaza and the old Plaza church. This streetcar could be running on either the O or B line. The B line would turn right at Macy St. (now Cesar Chavez Ave).
The next shot is one block north of the previous location. A B car inbound from Boyle Heights is turning left from Macy St. (now Cesar Chavez Ave.) onto North Main St. in 1948.