How do I find the counties in any given METAREA in ATUS-X?

How are the METAREA codes in ATUS-X generated? For example, in the 2010 sample code 1601 is labeled as Chicago-Naperville-Michigan City, but in the IPUMS-CPS codebook this is the code for the Aroura-Elgin PMSA.

My goal is to build a crosswalk between the METAREA codes in ATUS-X and the corresponding counties. Where can I get what I need for this?

The differences you see between the IPUMS-CPS and ATUS-X versions of METAREA are largely due to the differences in the grouping of metropolitan areas between the two surveys. Both follow a general coding structure related to the major metropolitan center (for both 160* implies a Chicago Area METAREA), but they diverge when sub-groupings include different components (IPUMS-CPS has never had a METAREA composed of Chicago-Naperville-Michigan City). You can use the State-based Metropolitan and Micropolitan Statistical Areas Maps from 2004 to determine the counties that make up the METAREAs from ATUS-X (aside from 2003) as the labels on the maps match those of the ATUS-X METAREA variable.

I hope this helps.