1. May 1, 1820: Maine became the 23rd state in the United States. The state was originally part of Massachusetts but separated and became its own state.

2. May 1, 1854: The first train arrived in Portland, Maine. The first passenger train from Boston arrived at the Grand Trunk Station in Portland, marking a significant moment in the state's transportation history.

3. May 1, 1862: The first battle of the Civil War was fought in Maine. The Battle of Yorktown occurred near the town of York in southern Maine, and although it was a small engagement, it was the first battle fought during the Civil War.

4. May 1, 1912: The first statewide referendum was held in Maine. The referendum was on a proposal to prohibit the sale, manufacture, and transportation of alcohol, and it was narrowly defeated.

5. May 1, 2004: Maine became the first state in the United States to ban the use of mercury in products. The ban covered a wide range of products, including thermometers, thermostats, and certain light bulbs, and was aimed at reducing the amount of mercury pollution in the state's waterways.