1. The first recorded landing by a European on the Hawaiian Islands occurred on August 21, 1778, when British explorer Captain James Cook and his crew arrived on the island of Kauai.

2. In 1959, Hawaii became the 50th state of the United States on August 21, after President Dwight D. Eisenhower signed the proclamation admitting Hawaii into the Union.

3. On August 21, 1959, Hawaii's first governor, William F. Quinn, was sworn in at ‘Iolani Palace in Honolulu, becoming the state's first governor as a U.S. state.

4. On August 21, 1968, the Mauna Kea Observatory, located on the island of Hawaii, was officially dedicated. It is home to some of the world's most powerful telescopes and is an important research center for astronomers.

5. In 1991, Hurricane Iniki, one of the most powerful hurricanes to ever hit Hawaii, made landfall on the island of Kauai on August 21. The storm caused extensive damage and was responsible for six deaths and over $1.8 billion in damages.