Communities across Missouri, Illinois, and Indiana were devastated by the deadliest and longest-running tornado ever recorded a century ago. Here's what happened.

A deadly tornado outbreak ripped through Missouri, Illinois, Arkansas and Mississippi overnight Friday, leaving destruction, power outages and tragic loss in its wake.

The deadliest twister in recorded U.S. history struck 100 years ago Tuesday, touching down in southeastern Missouri and tearing up everything in its 219-mile (352-kilometer) path for nearly four hours through southern Illinois and into Indiana.

Millions of Americans across the country are on alert for a severe weather outbreak as violent, long-track tornadoes with damaging winds of up to 80 mph and large hail are expected across the Midwest and South with the cross-country storm moving east.

A dangerous tornado outbreak which started on Friday evening continued into the first half of the weekend with nearly 2 dozen deaths across the nation's heartland and South.

Portions of West Virginia, Ohio and Pennsylvania were under a new tornado watch issued on Sunday by the National Weather Service, as the death toll from storms rose to at least 34 people in six states since Friday.