1. On June 20, 1839, Hawaiian King Kamehameha III declared a public holiday to celebrate the restoration of his kingdom's sovereignty after British intervention in 1843.

2. In 1893, on June 20th, the Hawaiian Constitutional Convention drafted a new constitution establishing a republic in Hawaii, following the overthrow of Queen Liliuokalani.

3. On June 20, 1902, the first inter-island wireless telegraph communication was established between the islands of Oahu and Kauai.

4. Duke Kahanamoku, Olympic gold medalist and surfing legend, was born on June 20, 1890, in Honolulu, Hawaii.

5. June 20, 1944, marked the beginning of the Battle of the Philippine Sea, one of the largest naval battles in history, as U.S. forces fought a Japanese fleet near the Mariana Islands. The battle also saw the first combat use of the F6F Hellcat, a carrier-based fighter aircraft developed in Hawaii.