Kinzua Bridge, Mount Jewett, McKean County, Pennsylvania

Destruction
On July 21, 2003, a tornado struck the Kinzua Bridge, snapping and uprooting nearby trees, as well as causing 11 of the 20 bridge towers to collapse. There were no human deaths or injuries. The tornado was produced by a mesoscale convective system (MCS), a complex of strong thunderstorms, that had formed over an area that included eastern Ohio, western Pennsylvania, western New York, and southern Ontario. The MCS traveled east at around 40 miles per hour (64 km/h). As the MCS crossed northwestern Pennsylvania, it formed into a distinctive comma shape. The northern portion of the MCS contained a long-lived mesocyclone, a thunderstorm with a rotating updraft that is often conducive to tornados.
At approximately 15:20 EDT (20:20 UTC), the tornado touched down in Kinzua Bridge State Park, 1 mile (1.6 km) from the Kinzua Bridge. The tornado, classified as F1 on the Fujita scale, passed by the bridge and continued another 2.5 miles (4.0 km) before it lifted. It touched down again 2 miles (3.2 km) from Smethport and traveled another 3 miles (4.8 km) before finally dissipating. It was estimated to have been 1⁄3-mile (0.5 km) wide and it left a path 3.5 miles (5.6 km) long. The same storm also spawned an F3 tornado in nearby Potter County.
Since 2002, the Kinzua Bridge had been closed to all "recreational pedestrian and railroad usage" after it was determined that the structure was at risk to high winds. Engineers had determined that during high winds, the bridge's center of gravity could shift, putting weight onto only one side of the bridge and causing it to fail. An Ohio-based bridge construction and repair company had already started work on restoring the Kinzua Bridge in February 2003. Construction workers had already packed up and were starting to leave for the day when the storm came.