1. Maine became a state on December 15, 1820: On this day, Maine was officially admitted as the 23rd state of the United States. The process of Maine's statehood was a result of the Missouri Compromise, which added Maine as the free state to maintain the balance between pro-slavery and anti-slavery states in the country.

2. The Great Bazaar Fire of 1866: On December 15, 1866, a tragic fire broke out in the Great Bazaar of Portland, Maine. The fire destroyed over a dozen buildings and resulted in the loss of millions of dollars in property. The incident led to the introduction of modern firefighting technology in Maine.

3. The Great Bangor Fire: December 15, 1911, marked the day when the Great Bangor Fire broke out, causing widespread destruction throughout the city. The fire destroyed over 250 buildings and caused the death of two people. The event led to the introduction of modern city planning and better construction standards in Maine.

4. The Judiciary Act of 1789: On December 15, 1789, the Judiciary Act was passed in the United States Congress. The act created the federal court system in the country, including the Supreme Court of the United States. The impact of the act was significant in Maine, as it provided a framework for the state's own judiciary system.

5. The Sinking of the Greenpeace ship Rainbow Warrior: In 1985, the Greenpeace vessel Rainbow Warrior was sunk by the French intelligence service in the port of Auckland. The ship was docked in Maine in 1982, where it played a crucial role in the opposition to nuclear power in the state. The event garnered worldwide attention and resulted in the expansion of environmental protection laws in Maine and throughout the world.