In that so-called Super Outbreak from Apr. 3-4, 1974, tornadoes were reported across 13 states, AccuWeather.com reported Thursday.
The latest figures from the National Oceanographic and Atmospheric Administration from Wednesday's outbreak reported 292 deaths, with 162 in Alabama alone.
NOAA estimated there were 173 tornadoes Wednesday, a record for a single storm system in modern times.
Fourteen states reported at least one tornado -- Tennessee, Ohio, Mississippi, Alabama, Arkansas, Missouri, Georgia, Virginia, Indiana, Maryland, South Carolina, North Carolina, Florida and New York.
Fatalities were reported in Tennessee, Virginia, Alabama, Georgia, Mississippi and Arkansas, AccuWeather.com reported.
More than 2,700 people stayed in Red Cross shelters Wednesday night, the organization reported.
At least 1 million people in Alabama were without power, with massive outages also reported in Tennessee and Georgia, while repairs to the Brown Ferry Nuclear Plant in Alabama could take weeks, officials said.
Wisconsin business offering 'therapeutic cuddling' forced to close
Campus cop fatally shoots Texas student during traffic stop