The northernmost and remotest of the Cook Islands atolls, Penrhyn was named after British explorer Captain William Crofton Sever’s ship the Lady Penrhyn (penrhyn = peninsula in Welsh), which passed by the islands in 1788. The Cook Islanders themselves called Penrhyn Tongareva, but continued contact (after Russian [Estonian!] Otto von Kotzebue first stopped by), particularly with the British, including annexation by same, and subsequent annexation by New Zealand, has led to the most common English name for the atoll to be Penrhyn, one of the Cook Islands’ dependencies in free association with New Zealand. There is an intriguing historical footnote wherein the United States of America made claim specifically to Penrhyn under its self-promoting and self-declared Guano Islands Act (of 1856, enabling United States of Americans to take possession, in the name of the United States of America, of unclaimed islands containing guano deposits; if Penrhyn was uninhabited at some point since 1856, it is only because the entire population was blackbirded into slavery elsewhere and/or perished from contact with colonizers/slavers - in this case, strangely, the Peruvians). Anyway, the United States of America eventually gave up claim to Penrhyn in 1980, some fifteen years after the Cook Islands had gained internal independence from New Zealand.
Stamp details: Top left: Issued in: 1920 From: Omoka, Penrhyn MC #20
Top right: Issued on: September 27, 1974 From: Penrhyn, Cook Islands MC #57
Stamps on bottom: Issued on: December 28, 2016 From: Penrhyn, Cook Islands MC #BL121
Recognized as a sovereign state by the UN: No Claimed by: Cook Islands (which, in turn, is in Free Association with New Zealand) Member of the Universal Postal Union: No