1. First South Dakota Governor Inaugurated - On April 6, 1889, Arthur C. Mellette was inaugurated as the first governor of South Dakota. He served as governor for four consecutive terms, making him the longest-serving governor in South Dakota's history.

2. Creation of the South Dakota State Capitol - In 1909, construction began on the South Dakota State Capitol Building in Pierre, which was completed in 1910. The building houses the offices of the governor and other state officials.

3. First Female State Senator Elected - On April 6, 1920, Nina Pettigrew was elected as South Dakota's first female state senator. She served in the South Dakota State Senate from 1921 to 1922.

4. First South Dakota Air National Guard Unit Activated - On April 6, 1948, the first Air National Guard unit in South Dakota was activated. The unit was based in Sioux Falls and consisted of P-51 Mustang fighter planes.

5. Rapid City Tornado - On April 6, 1972, an F4 tornado struck Rapid City, killing 238 people and causing over $160 million in damage. It remains one of the deadliest and costliest tornadoes in United States history.