Even 100 years later, the Tri-State tornado is widely considered America's worst tornado. It killed almost 700 in an era without warnings or radar.

The United States experienced other horrific tornadoes in the last century. More than 200 people perished in 1936 when Tupelo, Miss., was struck. More recently, more than 150 lives were lost and one-third of the city was destroyed when an F5 storm barreled through Joplin, Mo., in 2011.

Discover the devastating history of the Tri-State tornado, which spanned 219 miles, causing 695 deaths and 2,027 injuries across Missouri and Illinois.