1. On May 15, 1637, the Pequot War officially began in Massachusetts. This conflict was between the Pequot tribe, who controlled much of the area's fur trade, and the colonists, who wanted the same resources. The war lasted for nearly a year and resulted in the virtual annihilation of the Pequot people.

2. On May 15, 1817, the Massachusetts General Hospital was established. This hospital, which is still in operation today, was the third public hospital in the United States and one of the first to provide care for patients regardless of their ability to pay.

3. May 15, 1840, saw the introduction of the Massachusetts School for Idiotic and Feeble-Minded Youth. This was one of the first institutions in the country dedicated to providing specialized education and care for individuals with intellectual disabilities.

4. Taking a step back to 1762, another interesting event in Massachusetts' history took place. The first legal divorce in the state was granted on May 15th of that year. The couple in question had been married for 15 years, and the husband had been abusing his wife for much of that time.

5. More recently, May 15, 1954, marked the Supreme Court's decision in Brown v. Board of Education, which declared segregation in public schools to be unconstitutional. This landmark ruling was a major victory in the Civil Rights Movement and helped pave the way for greater equality and integration in the United States.