1. In 1864, the first territorial legislature of Montana convened in Bannack. This marked an important moment in Montana's history as it was the first official legislative assembly held in the territory.

2. On September 30, 1908, President Theodore Roosevelt declared the Lewis and Clark National Forest in Montana, which was the first national forest created in the state. Covering over 2 million acres, the forest is named after the famous explorers who traveled through the state in 1805-06.

3. The deadliest avalanche in Montana's history occurred on September 30, 1910, at the Wellington Mine near Taft. The avalanche killed 39 miners and brought national attention to the unsafe working conditions in the state's mines.

4. In 1935, a massive forest fire broke out in Montana and consumed more than a million acres of land. It became known as the "Bitterroot Fire" and was one of the most devastating wildfires in the state's history. The fire finally burned out on September 30, 1935.

5. September 30, 1963, marked the first day of operation for the Montana State University-Bozeman telescope, which was then the largest telescope in the world dedicated solely to research. It was instrumental in many astrophysical discoveries in the 1960s and 70s. Today, the telescope is still in use by researchers and students at MSU.