Editor's note: This story was originally published on November 10, 2015. It has been updated throughout to reflect the latest information.
This might be news to some LA natives, but referring to freeways with the definite article "the" is a thing that's unique to Southern Californians. Over at KCET, Nathan Masters says it all started because the region was an early adopter of the freeway.
In SoCal, routes were were given names as they opened, and the names corresponded to where the freeways ended or places they passed through—like the Arroyo Seco Parkway or the Hollywood Freeway.
The routes also had numbers assigned to them, but it wasn't uncommon for freeways in the LA area to have more than one route number attached to them. That meant that, for a time, the Pasadena Freeway was Route 6, 66, and 99.
Apparently, keeping track of all those numbers was as confusing as it seems, so people started to favor destination-based names of freeways. So the freeway that people took to get to San Bernardino was referred to as the San Bernardino Freeway instead of a jumble of numbers.
In 1964, the system for numbering the highways was streamlined statewide, so that each highway only had one number. Newer freeways, like the 605 Freeway, were being built around the same time, too, and so it suddenly became easier to call the freeway by its one, easy-to-remember number rather than its longer, more descriptive name.
But those wordy nicknames had already become a habit among SoCal residents, and it was still common to refer to freeways’ nicknames for years after the numbers were standardized. The enduring popularity of the nicknames led to the San Bernardino Freeway becoming known as the 10, and the Hollywood Freeway becoming the 101.
The habit was so firmly rooted that "Numbers only eclipsed names in common usage in the late 1970s," and the old names could still be read on Caltrans signs into the '90s, Masters says.
The intractable "the" is just further proof of how sticky those old names still are, Masters says.