Why is the ICAO prefix for Alaskan airports "P"? Mainland US airports all (to the best of my knowledge) have ICAO codes beginning with "K", however Alaskan airports all (from a couple of minutes rummaging about on FlightRadar24 and Flight Aware) seem to be prefixed with "P"?

Additional searching seems to indicate that Hawaiian airports are also prefixed with "P".
Definition from wikipedia:

The ICAO (/ˌaɪˌkeɪˈoʊ/, eye-KAY-oh) airport code or location indicator is a four-letter code designating aerodromes around the world. These codes are defined by the International Civil Aviation Organization, and published in ICAO Document 7910: Location Indicators are used by air traffic control and airline operations such as flight planning.

https://upload.wikimedia.org/wikipedia/commons/thumb/a/ab/ICAO_FirstLetter.svg/1200px-ICAO_FirstLetter.svg.png

This is a map of every ICAO airport code wordwide.

Alaska has PA, PF, PO and PP as airport codes. P = Eastern North Pacific.
PA=USA (Alaska) (also PF, PO and PP)

There is no special meaning behind the letter P and these codes, it's just a classification!!