Welcome to a great thread!I can tell you where UPS and AAA auto insurance (Auto Insurance of Northern CA and Southern CA) draw the line for the central coast area. We live in a small town called Lockwood (population 200). We can also get mail out of Bradley (population 93). If we use our Lockwood address (P.O. boxes only, no home delivery) we are in Northern CA. If we use our Bradley address (we have a mail box on a rural road and get home delivery for that address) we are in Southern CA. We had a choice to go with auto insurance through AAA of choosing Northern CA or Southern CA. The rates were cheaper in So. CA. Basically, if we want mail to go north, we send it through the Lockwood address. Their next major post office station is in Salinas. If we are sending mail to go south, we sent it through the Bradley address. Their next major post office is in Goleta. So, we must be on the border for the Central Coast. We have a phone number with a southern prefix. Our neighbors in either direction have a northern prefix. We were not allowed to get the northern prefix. All of the land lines are crossed up around here and our only provider, AT&T, decides who is in what area (northern or southern).