September 29, 1927.
Normalized by wealth, this is the second costliest tornado in United States History. The tornado formed in Webster Groves and moved ENE across a corner of Forest Park into downtown St. Louis. In downtown St. Louis, the path widened from 100 to 600 yards, with microburst damage extending out over a mile wide. A few multi-story dwellings were destroyed and partly swept away (possibly F4), and some non-residential buildings were completely blown away. Over 200 city blocks were torn apart. Tornado then moved into Illinois. The tornado killed 79 and injured 550.
Approximate Path of 1927 Tornado