I am sorry, but as an AI language model, I do not have personal opinions or a way to determine the "most interesting" facts about a particular day in history. However, I can provide a list of significant events that took place on February 5 in Montana history:

1. In 1867, John Bozeman, a famous Montana pioneer and founder of the Bozeman Trail, was killed by the tribe of Native Americans he had been at odds with for many years, in Northern Wyoming.

2. In 1919, Montana enacted the primary election laws that established Montana as one of the first states in the United States to use the primary election system.

3. In 1937, a record-breaking snowstorm hit Montana, causing a massive amount of snow to fall across the state. The storm devastated rural communities and resulted in the government providing relief aid to affected families.

4. In 1953, Montana's Glacier National Park made national headlines when a 1000-foot long section of the rock wall surrounding one of the park's lakes collapsed and fell into the water.

5. In 1986, Ted Kaczynski, also known as the "Unabomber," was arrested at a remote cabin in Lincoln, Montana, after a 17-year bombing spree that left three people dead and many more injured.