1. Kilauea volcano erupts in 1926: On May 20, 1926, Kilauea volcano on the Big Island of Hawaii erupted with a massive explosion that sent clouds of ash and smoke into the air. This eruption lasted for over two weeks and was one of the most significant in the volcano's recent history.

2. Queen Liliuokalani's birthday: May 20 is the birthday of Queen Liliuokalani, the last reigning monarch of the Kingdom of Hawaii. She was born in 1838 and ruled from 1891 to 1893 when she was overthrown in a coup d'état.

3. Hawaii becomes a US Territory: On May 20, 1898, Hawaii officially became a US Territory after an annexation treaty was signed between the United States and the Hawaiian government. This move was controversial at the time and has had a significant impact on Hawaii's history and culture.

4. Hawaii's only Medal of Honor recipient: On May 20, 1944, Private Barney Hajiro of the US Army's 100th Infantry Battalion became the first person of Japanese ancestry to receive the Medal of Honor, the highest military decoration awarded by the US government. Hajiro was born in Hawaii and served in Italy during World War II.

5. Hōkūleʻa's maiden voyage: On May 20, 1976, the Hōkūleʻa, a traditional Polynesian double-hulled voyaging canoe, set sail on its maiden voyage from Hawaii to Tahiti. The voyage was a re-creation of ancient Polynesian navigation techniques and helped to revive interest in traditional Hawaiian culture and seafaring.