Century Boulevard was planned to run from Los Angeles Airport to Santa Ana. The name was chosen because it runs along the 10000 S (which would make it 100th St) line for Los Angeles housing numbers. The section in Los Angeles and Inglewood was originally named Pine Avenue or San Antonio Street. The street extends only as far east as Watts, and then it peters out.
There is another street formerly known as Century Blvd in Lynwood, which has now been renamed Martin Luther King Jr Blvd. This street would extend across the Los Angeles River, where there are two short segments of Century Blvd in Paramount. This street would have continued, and followed a diagonal course parallel (and possibly adjacent) to the Pacific Electric tracks. There are also two short segments of Century Blvd in Garden Grove and in Santa Ana.
Imperial Hwy seems to have been mostly complete from the Los Angeles-El Segundo border to Anaheim by 1935. In most of Los Angeles it runs at the latitude of 11400, which would make it 114th St, but jogs down to 116th St near Central Ave. The 114th St portion was once known as Bellevue Ave, at least in El Segundo.
El Segundo Bl was known as El Segundo Ave in El Segundo, then Ballona Ave or 128th St in Los Angeles. It terminates at Alpine Av in Lynwood. The plan was to have it connect with Burton Av and then Carlin Av, and then deviate south to meet Rosecrans Ave just west of the Los Angeles River. But the cities of Lynwood and Compton declined to make this last connection.
Rosecrans Ave. Named for Civil War General William Starke Rosecrans (1819-1898), who settled in Redondo, and owned what became known as the Rosecrans ranch.
In Compton, Rosecrans Ave was once known as Orange St, and in Clearwater (now Paramount) as State St.
Further east, Rosecrans Ave is the former Washington St in Bellflower. (Washington St at that time ran westward into Clearwater after jogging south about a half mile to run over the present course of Compton Blvd.)
Marine Av-Compton Bl-Somerset Bl. This street was intended to be a continuous east-west highway, connecting Manhattan Beach with Norwalk. The portion connecting Gardena with Compton across the Los Angeles shoestring was never built.
The Manhattan Beach segment was once called Chicago Avenue, and later renamed Marine Avenue.
The segment in Lawndale and Gardena, originally Amestoy Street, was named Compton Boulevard, in anticipation of the connection with the Compton segment. As the city of Compton acquired a somewhat undesirables reputation, the city of Lawndale renamed its portion Marine Ave. Later Redondo Beach and Gardena followed suit.
The Compton segment was originally named Main Street, and is the division of the street numbering system between north and south.
The segments in Paramount and Bellflower were originally called Washington Street, and then renamed Compton Blvd, but Paramount, perhaps trying to dissociate itself from Compton, renamed its portion Somerset Blvd. Later Bellflower followed suit. (Bellflower Blvd was at one time called Somerset Blvd.)
Washington Street was part of a series of streets named for U.S. Presidents, in the settlement known as Clearwater (now Paramount). Washington St continued into Bellflower, and followed the course of Fleming Avenue northward, and then along the only remaining segment still called Washington St. Then the Washington Street name went north on Woodruff Ave, and then east on what is now Rosecrans Ave.
This street is at the latitude of Excelsior Ave in Norwalk, but the bridge across the San Gabriel River was never built.
This is one street which went from one name to three, contrary to what planners intended in the 1930s.