What are the biggest tornadoes in the US?

Answer 1

Some of the largest tornadoes on record in the U.S. are:

1. The Hallam, Nebraska tornado of May 22, 2004. This massive F4 tornado was, at one time, 2.5 miles wide. It is commonly state as the widest tornado on record
2. The Mulhall, Oklahoma tornado of May 3, 1999. This F4 tornado is usually overshadowed by the smaller but more intense tornado that struck Oklahoma City on the same day. Doppler Radar indicated that the tornado may have been as much as 4 miles wide, but evidence in the damage path could not confirm this.
3. The Seneca, Kansas tornado of May 17, 1896. The F5 tornado, which devastated several towns in Kansas, was over 2.2 miles wide at one point.
4. The Moshannon State Forest, Pennsylvania of May 31, 1985. This F4 tornado was part of the most intense tornado outbreak to strike the northeastern U.S. It carved a damage path at least 2.2 miles wide through the forests of central Pennsylvania.