ISO 3166-2:US is an ISO standard which defines geocodes: it is the subset of ISO 3166-2 which applies to the United States of America. It covers 50 states, 1 district, 6 outlying areas (including 9 minor outlying islands under separate ISO 3166-1country code UM). The second part of the code is two-letter alphabetic, and, except for UM, is the same as the U.S. postal abbreviation.