1. Statehood Day: May 1st is recognized as Statehood Day in South Dakota, as it marks the anniversary of the state's admission to the Union in 1889.

2. First Capitol: On May 1, 1889, the first session of the South Dakota State Legislature was convened in the city of Pierre, which became the state capital three years later.

3. Homestake Mine: A significant moment in South Dakota mining history occurred on May 1, 1942, when Homestake Mine in Lead became the largest gold producer in the country. The mine would continue operations until 2002.

4. Immigration: May 1, 1907, was the deadline for immigrant registration in the state of South Dakota, as part of a federal effort to document and regulate the influx of foreign workers to the United States.

5. Labor Day: While not specifically related to South Dakota, May 1 is recognized worldwide as International Workers' Day, a holiday honoring the labor movement and workers' rights. In the United States, Labor Day is celebrated on the first Monday in September.