What NFL running back has the highest average yards per carry for a single season?

That would be Beattie Feathers of the 1934 Chicago Bears who had 119 rushing attempts for 1004 yards and an 8.4 (8.437) yards per carry average. That was tied in 2006 by Atlanta Falcons QB Michael Vick who had 123 rushing attempts for 1039 yards and an 8.4 (8.447) yards per carry average.