What do you think was the most interesting event in Montana history?

For the past couple of weeks, my husband and I have been discussing what we thought were the most interesting events in Montana history.  We both agreed that the discovery of gold, the arrival of the railroads and the activities of the vigilantes both in the gold camps and later in central Montana were all interesting, but I have been wondering what others would include in that list.  So how about it, what do you think is the most interesting event in Montana history.  Please respond in the comment section.  I will share the results.