Author: Alan, 5B4AHJ
Canton (aka Kanton) Island and Enderbury Island were the subject of a dispute between Britain and the USA from 1937-39, with both countries claiming sovereignty over the islands.
The dispute was resolved amicably on 1939-04-06, when Britain and USA agreed to jointly control the islands for the next forty years, as the Canton & Enderbury Islands Condominium.
The result of this agreement was that both Britain and the USA issued operating permits for amateur radio operation from the islands.
British operations used the VR1 prefix, and American operations used the KB6 prefix in the period immediately post-WWII (1945-46 or 47) followed by KB6 until 1978-03-23, after which KH1 was used until 1983-09-23.
The bizarre consequence of this, from a DXCC perspective, was that British operations from these islands counted as British Phoenix Islands (now Central Kiribati), whereas American operations counted as Baker, Howland & American Phoenix Islands!
The Republic of Kiribati was formed on 1979-07-12. The new republic included Canton & Enderbury Islands, at which time the Anglo-American condominium was formally terminated. However, the Treaty of Tarawa, in which the USA relinquished all claims to Canton and Enderbury Islands, did not come into force until 1983-09-23.
Since 1979-07-12, all QSOs with Canton and Enderbury Islands count for Central Kiribati, except for stations with a KH1 callsign before 1983-09-23. Examples of KH1 callsigns in this period are KS6DV/KH1 in 1979 and SM0AGD/KH1 in October, 1982.
Following the relinquishing of US claims to Canton Island, there was some discussion in ARRL as to whether to delete the entity of Baker, Howland & American Phoenix Islands and replace it with a new entity, Baker & Howland Islands, or simply to rename the existing entity. The decision was made to go for the renaming option.
RSGB DX News Sheet
Wikipedia Kanton Island
Wikipedia Treaty of Tarawa