As an AI language model, I cannot guarantee the accuracy of historical events. However, based on available data, here are 5 interesting facts related to January 21 in Montana history:

1. In 1881, the territorial legislature voted to move the capital of Montana from Virginia City to Helena. The decision was made on January 21 and marked the end of a long debate between the two cities.

2. January 21, 1909, saw the formation of the Montana Woolgrowers Association, which became one of the oldest and most influential livestock organizations in the state.

3. On January 21, 1911, the famous mountain climber Norman Clyde completed the first winter ascent of Granite Peak, the highest peak in Montana. The climb was considered one of the most significant mountaineering achievements in the United States at the time.

4. January 21, 1924, marked the opening of the famed Northern Pacific Railway passenger service from Minneapolis to the west coast. The railway was a significant transportation route for Montana, connecting the state to the rest of the country.

5. In 1987, Montana State University quarterback Kelly Bradley was drafted by the New York Giants in the 11th round of the NFL draft on January 21. Bradley would go on to a successful career in the Canadian Football League.