1. On September 12, 1862, General William Tecumseh Sherman assigned the Seventh Infantry to Yellowstone and the surrounding areas for the purpose of maintaining peace with the Native American tribes who lived in the region. This assignment was aimed at protecting the pioneers who were moving out West during this time.

2. On September 12, 1900, the last of the Plains Indian wars ended when Chief Joseph of the Nez Perce tribe surrendered to the US Army in Montana. The conflict, which lasted over 15 years, resulted in the displacement and relocation of thousands of Native Americans from their ancestral lands in the West.

3. On September 12, 1966, the Montana Power Company began construction on the Colstrip Power Plant, which would become one of the largest coal-fired power plants in the United States. The plant was planned to help meet the growing demand for electricity in the Western states.

4. On September 12, 1986, the Montana State Capitol building in Helena was added to the National Register of Historic Places. The building was completed in 1902 and is one of the most iconic examples of neoclassical architecture in the state.

5. On September 12, 2008, the Montana Supreme Court ruled to overturn a state law that limited the rights of same-sex couples. The decision was a landmark moment in the fight for marriage equality and set the stage for other states to follow suit in recognizing the right of all couples to marry regardless of gender.