zip_codes_for_the_us contains GeoJSON files of U.S. zip codes grouped by their Metropolitan Statistical Area (MSA). The files were created using a TopoJSON of U.S. zip codes assembled by Jeff Friesen and a table created by the Department of Labor Office of Worker's Compensation which matches zip codes with corresponding MSA numbers.
Note that MSA.tsv is a cleaned version of the original table. The accuracy of certain statistical analyses may be limited by the resolution of the original TopoJSON file.