A version of the GSM protocol that runs in the USA 800MHz "Cellular" band was releaed in the year 2002. Prior to this, GSM in the USA only ran in the 1900MHz PCS band.

The USA 800MHz Celluar band consists of the frequency ranges of 824.01-848.97MHz and 869.01-893.97MHz. This band has always been referred to as the "800MHz" Cellular band (for instance CDMA and IS-54 systems running in this band would be called CDMA800 and TDMA800). However, the version of GSM that runs in this band is being called GSM850 rather than what would be expected: GSM800.

It is true that the "800MHz" Cellular band does actually include the frequency 850.00MHz and not the frequency 800.00MHz, but it seems a little late in the game to try to change the nomenclature now, when everyone is used to referring to the "800MHz" band.

In any event, GSM850 systems do actually run in the standard 800MHz Cellular band, and the terms GSM800 and GSM850 can be used interchangably. On this site, I will use the term GSM800 or GSM 800MHz in order to avoid confusion.