Gore, 33, entered the game needing just 37 yards to top the milestone. Riggins, the longtime Washington Redskins running back, rushed for 1,239 yards in 1984 at the age of 35.
Gore is also the first Colts running back to rush for at least 1,000 yards in a season since Joseph Addai gained 1,072 yards in 2007.
Gore's play this season continues to defy those that say he's slowing down at his age. He put up most of his rushing yards behind a Colts offensive line that has started two or three rookies up front for most of the season. He has passed Jim Brown, Thurman Thomas, Franco Harris, Marcus Allen, Edgerrin James, Marshall Faulk and Tony Dorsett -- six of the seven are in the Hall of Fame -- to move to eighth on the NFL's all-time rushing list this season.
"Me growing up and me hearing a lot of what I couldn't do," Gore said. "When I got to 28, I heard I was on my last leg. That just motivated me to keep going. I never let a man judge me. I believe in the man up above. As long as he has my body feeling great, I train hard in the offseason and I still love the game, I'm going to come back and play as hard as I can."