1. Montana officially becomes a state: On December 17, 1889, Montana became the 41st state of the United States. The territory gained statehood after its constitution was ratified by the US Congress.

2. The first woman elected to Congress: On December 17, 1916, Montana native Jeanette Rankin was elected to the US House of Representatives. She was the first woman to hold national office in the United States.

3. Deadly train derailment: In 1943, a train carrying military personnel derailed near Helena, Montana, resulting in the deaths of at least 32 people. The accident was caused by a landslide and is one of the largest train disasters in Montana's history.

4. Record-breaking snowstorm: In 1996, a record-breaking snowstorm hit Montana on December 17th. The state received over 2 feet of snowfall in just 24 hours, leading to transportation disruptions and power outages.

5. Montana gains a new national forest: On December 17, 1906, President Theodore Roosevelt created the Lewis and Clark National Forest in Montana. The forest covers over 1 million acres and is named after the famous explorers who traveled through the area.