In downtown San Diego, why are First through Twelfth called avenues and the rest called streets?

Dearest Matthew:

Why are only the first 12 numbered streets in downtown San Diego called "avenue," the remainder "streets"? My speculation is that rather than messing up traffic by eliminating the [bad luck] designation 13, the rational dudes said, "Hey, if we call it 13th Street after a series of avenues, it's really not the 13th avenue, but the first street. Thus the bad karma of the number 13 will be disrupted." Or sump'n like that... Am I full of it or am I some kinda freakin genius?

-- Neil Allen, San Diego

Some kinda freakin sump'n, Neil. Not sure quite what, though. Heck of a theory. But let's hop on the way-back trolley and get off at June 8, 1931. That's the day Mrs. Martin German presented the city council with a request to change the name of First Street to First Avenue. In two weeks, City Ordinance #13237 was passed unanimously. It changed all the names, from First through Twelfth, from streets to avenues. It turns out that Mrs. German was chairman of the First Street Bridge Committee. Her motives? Perhaps lobbying for a bridge to connect the uptown and downtown portions of First Street in Hillcrest. A name change to First Avenue might make the street (and thus the project) sound more important?

A surprisingly snide newspaper report on June 16 gives our only other clues. "Eleven San Diego streets may attain to whatever distinction rests in the name of 'avenue' under plans set on foot by the city council yesterday... Fifth already rejoices in the avenue title... Manager Gregory added that if First [and Fifth were] to be avenues, he would recommend that all streets from First to Twelfth be called avenues." One councilman huffed about 13th and the rest being left out, so they promised to look into it later. Yeah. Sure. First through Twelfth are the only downtown streets that extend, uninterrupted, north of Balboa Park, so they were taken care of first.

When the writer referred to Fifth already rejoicing in the name-- Fifth Street wasn't officially Fifth Avenue before 1931. It was just a major business thoroughfare in the heart of the city and had acquired the "avenue" designation unofficially, maybe in imitation of Fifth Avenue in New York.