As an AI language model, I do not claim to be perfect in my understanding of historical events. However, here are five interesting facts about October 5 in Massachusetts history:

1. In 1789, the cornerstone of the Massachusetts State House was laid in Boston. The building, designed by architect Charles Bulfinch, has become an iconic symbol of the state.

2. In 1830, the Boston Society for the Diffusion of Useful Knowledge was established. This organization sought to promote education and enlightenment among the citizens of Boston.

3. In 1864, Hopkinton, Massachusetts became the starting point for the Boston Marathon. The race, which is now one of the most prestigious marathons in the world, attracts thousands of runners every year.

4. In 1903, Harvard University's Widener Library opened to the public. The library, which contains over 3.5 million volumes, is one of the largest libraries in the world.

5. In 1995, the Boston Red Sox played their final game at Fenway Park before renovations began. The historic ballpark, which has been home to the Red Sox since 1912, underwent an extensive renovation project that lasted two years.