Geography of the USA
There are 50 States, 15 Divisions, 71 Sections, 3077 Counties (Link will open in your Browser), 41 Independent Cities, 16 Territories (Link will open in your Browser), 14 QSO Multiplier Regions for HI,
and the District of Columbia, which is neither a State, Section (though it is a member of MDC), or County, but a District that is used as a multiplier in the MDC QSO Party.
It doesn't contain any Counties either, though it used to have 2.
Of the 50 States, 48 are contiguous: these are often known as the 'Lower 48', or 'CONUS'. They all count as the 'United States' for DXCC purposes. The remaining 2 states are Alaska (AK), and Hawaii (HI), which both count as separate country-entities.
There are 83 Sections in total, comprising of: Alaska, Hawaii and Pacific territories, US Virgin Islands, Puerto Rico, 12 in Canada, and 67 in Continental USA.
The U.S. currently has sixteen territories (Link will open in your Browser) in the Caribbean Sea and the Pacific Ocean. Five (American Samoa, Guam, the Northern Mariana Islands, Puerto Rico and the U.S. Virgin Islands) are permanently-inhabited, unincorporated territories; the other nine are small islands, atolls and reefs with no native (or permanent) population. Of the eleven, only one is classified as an incorporated territory (Palmyra Atoll). Two territories (Bajo Nuevo Bank and Serranilla Bank) are de facto administered by Colombia.
The United States Minor Outlying Islands (Link will open in your Browser) are small islands, atolls and reefs. Palmyra Atoll, Baker Island, Howland Island, Jarvis Island, Johnston Atoll, Kingman Reef, Midway Atoll and Wake Island are in the Pacific Ocean, and Navassa Island, Serranilla Bank, and Bajo Nuevo Bank are in the Caribbean Sea. Palmyra Atoll (formally known as the United States Territory of Palmyra Island) is the only incorporated territory, a status it has maintained since Hawaii became a state in 1959.
For County-Hunting purposes the Territories are not included. American Samoa does have its own counties, but the U.S. Census Bureau does not count them as counties (instead, the U.S. Census Bureau counts American Samoa's 3 districts and 2 atolls as county equivalents). American Samoa's counties are treated as minor civil divisions. Most territories are directly divided into municipalities or similar units, which are treated as equivalent of counties for statistical purposes:
The 78 municipalities of Puerto Rico
The 3 main islands of the United States Virgin Islands
All of Guam
The 4 municipalities of the Northern Mariana Islands
The 3 districts of American Samoa
The 2 atolls of American Samoa
The 9 islands of the U.S. Minor Outlying Islands
The U.S. Census Bureau counts all of Guam as one county-equivalent (with the FIPS code 66010), while the USGS counts Guam's election districts (villages) as county-equivalents. The U.S. Census Bureau counts the 3 main islands in the U.S. Virgin Islands as county-equivalents, while the USGS counts the districts of the U.S. Virgin Islands (of which there are 2) as county-equivalents.
Not all States have Counties: Alaska has 19 organized Boroughs, and one unorganized borough which encompasses nearly half of Alaska's land area, an area larger than any other U.S. state. It is divided into 10 census areas:
Aleutians West, Bethel, Dillingham, Hoonah-Angoon, Kusilvak, Nome, Prince of Wales - Hyder, Southeast Fairbanks, Valdez-Cordova, Yukon-Koyukuk. For County-Hunting purposes, Alaska is divided into 4 regions.
One State uses additional regions to its counties in its QSO Party: the US State of Hawaii has five counties which are used for 'County Hunting' activities. However, for the purposes of the annual Hawaii QSO Party, the state is split into 14 regions, based on zipcode regions. These have recently been re-defined and mapped.
Other States also have Boroughs: Connecticut, New Jersey, New York, Pennsylvania, and Virginia, where Boroughs may be the same as the existing (i) cities, (ii) counties, or (iii) portions of such counties. None of this applies to County-Hunting.
The U.S. state of Louisiana is divided into 64 parishes - these are classed as Counties for County-Hunting purposes.
Are there any parts of the USA that don't count for County-Hunting? Yes: District of Columbia, the 41 Independent Cities, and the 16 Territories.