jargon

So I've noticed that in Southern California, the lingo requires that you put a "the" in front of all highway names. So whereas in Ohio, we say "take I-75 until you get to the exit for 475"... here people talk about "the 5" or "the 101."

Why is that? And is it strictly a SoCal thing-- as this Wikipedia article might lead one to believe-- or do people do it elsewhere too?

It's kind of a hard question to Google.

And now, a slightly-related video! (Song introduced to me by my youngest sis-in-law when she burned me a pair of birthday CDs. Thanks, Clare!)

LINK BECAUSE THE VIDEO CAN'T BE EMBEDDED