Zip codes are trees, each digit narrows down the area. The final area can be non-contiguous, but 92014 is entirely contained within 9201, that's within 920, etc

Zip codes are trees, each digit narrows down the area. The final area can be non-contiguous, but 92014 is entirely contained within 9201, that's within 920, etc. up to 9, which is the US west coast area.