Islands were discovered by Captain Cook in 1773-5; he named them the Hervey Islands after the then First Lord of the Admiralty. The group was proclaimed a British protectorate in April 1888 and formal possession was taken in 1900. By Order in Council of 13 May 1901 Cook Islands were placed under New Zealand control and they have remained so ever since. Rarotonga is the principal island and the administrative centre of the group.

Postal History
As with many of the Pacific islands, contact with the outside world was originally maintained by missionaries who first started missions in the islands in 1821. At that time, letters were carried by the few ships which called occasionally at the islands, but there is evidence that these were coordinated by the British consulate.

Under the British protectorate, stamps were issued and these were used at Rarotonga, which was the only P0 open at that time. Mangaja P0 on a neighbouring island was opened in 1903.

Stamps of Cook Islands were inscribed 'Rarotonga' from 1919 to 1932, but reverted to 'Cook Islands' when Aitutaki and Penrhyn were included in the group and their separate issues withdrawn (see also Aitutaki, Niue and Penrhyn islands). Eight POs within the group were operating by 1935.