1. May 1, 1637: The Massachusetts General Court passed a law establishing a military training day known as "Muster Day." This day required every able-bodied male aged 16 or older to bring their own weapon, ammunition, and provisions to a designated location for a day of training.

2. May 1, 1766: Boston's Haymarket Square was completed as the city's first public market, which quickly became a center of commerce and trade for the rapidly growing city.

3. May 1, 1786: Shays' Rebellion, a populist uprising of debt-ridden farmers and revolutionary war veterans, came to a head in Massachusetts. The rebellion prompted calls for a stronger federal government and ultimately led to the drafting of the US Constitution.

4. May 1, 1865: The Massachusetts 54th Infantry, one of the first all-black units in the US Army, participated in the Union Army's Grand Review parade in Washington D.C. after the end of the Civil War. The unit had played a significant role in the war and was recognized for its bravery and valor.

5. May 1, 1897: The Massachusetts legislature officially recognized May Day as a state holiday, making it one of the first states to do so. Since then, May Day has been celebrated throughout the state with parades and festivals, often featuring traditional New England Maypole dancing.