Zipcode - State Relationship

One approach would be to use the ZIP-County crosswalk provided by the Department of Housing and Urban Development.

www.huduser.gov/.../usps_crosswalk.html

Counties are entirely nested within states, so you could use the crosswalk to match each ZCTA to a set of counties and then check which state those counties belong to. This would give you a mapping between ZCTAs and states.

Here's a list of the relationships between states and counties (each uniquely identified by FIPS codes).

www.census.gov/.../2017-fips.html

One approach would be to use the ZIP-County crosswalk provided by the Department of Housing and Urban Development.

www.huduser.gov/.../usps_crosswalk.html

Counties are entirely nested within states, so you could use the crosswalk to match each ZCTA to a set of counties and then check which state those counties belong to. This would give you a mapping between ZCTAs and states.

Here's a list of the relationships between states and counties (each uniquely identified by FIPS codes).

www.census.gov/.../2017-fips.html

Thanks for the clear explanation and useful links.