Jul 21, 1987
A 1.5 mile-wide EF4 tornado churned through Yellowstone National Park for 24 miles. Over 1 million trees were uprooted and discarded by this rare high altitude tornado, the highest ever recorded. The tornado began at roughly 7,000 feet above sea level and then climbed several thousand feet to crest at over 10,000. Despite no injuries, fatalities and limited infrastructure damage, the tornado was responsible for $2.5 million in damage.