1. Montana became a state: December 6, 1889, marks the day Montana became the 41st state in the United States of America.

2. Chester A. Arthur became President: On December 6, 1881, Chester A. Arthur became President of the United States after the assassination of James A. Garfield.

3. Montana State Capitol fire: On December 6, 1935, the Montana State Capitol building in Helena caught fire and was destroyed. The building was subsequently rebuilt and reopened in 1942.

4. Yellowstone National Park expanded: On December 6, 1929, Congress approved the expansion of Yellowstone National Park in Montana, adding 49,000 acres to the park.

5. Copper King Mansion: William A. Clark, the notorious Copper King of Montana, died on December 6, 1925. His impressive mansion in Butte, now known as the Copper King Mansion, is on the National Register of Historic Places and is open for tours.