1. In 1863, the Battle of Gettysburg began in Pennsylvania, and soldiers from Massachusetts played a major role in the Union's victory. The 10th Massachusetts Regiment suffered heavy losses during the battle but played an important part in holding the Union center on the second day.

2. In 1895, the Massachusetts Institute of Technology (MIT) was incorporated. MIT has become one of the most prestigious universities in the world, known for its research in science, engineering, and technology.

3. In 1944, the United States Navy commissioned the USS Valley Forge, an Essex-class aircraft carrier. The ship was built in Quincy and named after the winter encampment of General George Washington's army in Pennsylvania.

4. In 1953, Julius and Ethel Rosenberg were executed for espionage, accused of providing atomic secrets to the Soviet Union. The case was highly controversial and sparked international condemnation, with many accusing the government of using the Rosenbergs as a scapegoat for anti-Communist sentiment.

5. In 2013, same-sex marriage became legal in Massachusetts, following a landmark Supreme Judicial Court decision in 2003 that declared the state's ban on same-sex marriage unconstitutional. Massachusetts was the first state in the country to legalize same-sex marriage, paving the way for similar laws in other states.