The majority of tornadoes in the United States stay on the ground for less than 5 miles. It is unusual for tornadoes to have a path of longer than 30 miles. Many of the longest tornado damage paths are caused by multiple tornadoes from a tornado family, rather than by a single tornado. Very few single tornadoes have been confirmed with paths of longer than 100 miles.
The Tri-State Tornado
This devastating tornado of March 18, 1925, had the longest tornado path of any documented tornado in the United States. Its total track measures at least 219 miles, and may have been as long as 234 miles. Although there is some controversy over whether the Tri-State Tornado was a single tornado or a family of tornadoes, recent research confirms that it was most likely a single tornado.
The Tri-State Tornado was originally thought to have started near Ellington, Missouri. However, Red Cross records and eyewitness accounts show that the Tri-State Tornado began roughly 15 miles earlier, in Shannon County. From there, the tornado continued all the way across the narrow part of southern Illinois to as far east as Pike, Indiana. The power of the Tri-State Tornado was never officially rated, but the recorded damage is equivalent to an F5 tornado.
The path is so long partly because the Tri-State Tornado was on the ground for a long time and partly because it was moving unusually fast. In total, the Tri-State Tornado was on the ground for at least 3-1/2 hours. Throughout that entire time, it averaged a ground speed of 62 miles per hour.
The Tri-State Tornado happened long before the first successful forecast of a tornado. Its high ground speed, combined with a debris and mist cloud which hid the main funnel, meant that many people were caught by surprise. At least 695 people were killed. The Tri-State Tornado is still the deadliest tornadoes in U.S. history.
The Monticello, Indiana tornado
The Monticello F4 tornado of April 3, 1974, was part of the Super Outbreak, the second largest burst of tornado formation on record. It was on the ground for 109 miles, nearly crossing the entire state of Indiana. Together with other tornadoes which formed along the same track, the total damage path of this tornado family was roughly 121 miles.
Better tornado forecasting reduced the number of casualties, but even so, 18 people were killed directly by the tornado, with another person killed by related storm damage. The path of this tornado also contradicted the tornado myth that tornadoes will not descend hills into steep valleys. At one point, the path was 1/2 mile wide.
Super Outbreak II
In the American Southeast, 359 tornadoes were documented between April 25 and 28, 2011. Several of these were long-track tornadoes, including the Cordova-Blountsville EF4 tornado (128 miles) and the Tuscaloosa-Birmingham EF4 tornado (81 miles). The longest tornado path during this outbreak belonged to the Hackleburg-Huntland E5 tornado, which caused 132 miles of devastation.
All 3 of these tornadoes hit Alabama on April 27, the most severe day of the outbreak. Together, they killed 149 people, nearly half of all the tornado deaths during the outbreak. The outbreak as a whole caused more damage than any other tornado event in U.S. history, and April 2011 has gone down as the most active tornado month since record keeping began.
The Charleston tornado family
Before tornado families were known to exist, the tornado cluster of 1917 in Indiana and in Charleston and Mattoon, Illinois, were thought to be a single tornado with a record damage track at least 293 miles long. This tornado family still holds the record for the longest tornado damage track by a single tornado family.