The largest width for the day is 900 yards from an F3 tornado that crossed through parts of Union County, AR in 2005. The path length was 24 miles. 13 injuries and 2 fatalities were reported.
The NWS Summary states, "The tornado that moved through Claiborne Parish Louisiana moved northeast into Union County Arkansas." I researched the Claiborne Parish tornado, the official end point is over Lake Claiborne well south of the Arkansas line. Here is the NCDC report on that separate tornado.
Per the NWS Summary, some of the worst damage was found in the area from Tatum Rd, across Hwy 7 and into the vicinity of Rushwood Rd. It was in the area of Tatum Rd through Rushwood Rd that two fatalities occurred, both of them elderly residents.
Full summary below the map.