The largest width for the day is 500 yards from an F1 tornado that tracked through parts of Dougherty County, GA in 1966. The path length was 0.5 miles. There was 1 reported injury.
We gathered information for this event from the SPC & NCDC Databases and the February 1966 Storm Data Narrative:
The only small difference was that the Storm Data summary did not have a path length listed.