Zip code/Zip code tabulation area crosswalk

Try this. Go to the link below and weed out the ones on your list that are POBoxes and "Unique" (the "unique" are pretty much the businesses/universities that have their own zip code).
www.zip-codes.com/.../ca-los-angeles.asp

I dont think you'll find a crosswalk because of the changing nature of zip code boundaries. They are somewhat "fluid" because zip codes are created by the USPS for the purpose of delivering mail, so their boundaries change as carrier routes get adjusted.

If you haven't already, it may also be helpful to read these items about ZCTAs and how they are created and how they compare to zip codes.
How ZCTAs compare to zip codes:
www.census.gov/.../zcta.html

ZCTA documentation:
www.census.gov/.../zctas.html

Try this. Go to the link below and weed out the ones on your list that are POBoxes and "Unique" (the "unique" are pretty much the businesses/universities that have their own zip code).
www.zip-codes.com/.../ca-los-angeles.asp

I dont think you'll find a crosswalk because of the changing nature of zip code boundaries. They are somewhat "fluid" because zip codes are created by the USPS for the purpose of delivering mail, so their boundaries change as carrier routes get adjusted.

If you haven't already, it may also be helpful to read these items about ZCTAs and how they are created and how they compare to zip codes.
How ZCTAs compare to zip codes:
www.census.gov/.../zcta.html

ZCTA documentation:
www.census.gov/.../zctas.html

We are fortunate in SE Michigan because about 20 years ago the ZIP codes were redone in some counties and aligned with our city/township (MCDs here) geography. That makes the boundaries consistent. However, it's certainly true that often it's unclear where a zip code boundary actually is. But...Census can define them through the reported zip codes of addresses on the MAF, so that should generally lead to consistency even when they're hard to map.

In general, addressing throughout the nation has improved greatly in the past 25-30 years because of the 911 systems' requirements. That's why rural areas got addresses instead of rural route/box numbers. The ambulance has to be able to find the house!

Patty, you wrote "But...Census can define them through the reported zip codes of addresses on the MAF"
Are you saying the US Census Bureau can define boundaries of ZIP codes? I know they have boundaries for ZCTAs, but having boundaries for ZIP codes, I didn't know that.

Gene - well, yeah, they can outline them to a close approximation. For ZCTAs, they round them to block boundaries because the data are tabulated from blocks, not from electronic maps. I don't think they've ever published those lines, but I'm sure they know where they are and where they overlap. But that's why I don't worry about the correspondence between Zips and ZCTAs.

JamiRae thanks again for your suggestion. I went through that website and compared the ZCTA list with those zip codes and you were right. Most of the missing ZCTAs were for PO Boxes and Unique zip codes. Thanks again!!