Summing was a bay horse bred in Kentucky by his owner Charles T. Wilson Jr.
He was sired by Verbatim, a leading dirt performer whose wins included the 1969 Whitney Stakes.
Summing's dam Sumatra was a high-class racemare whose wins included a division of the Santa Ysabel Stakes.
Trained by Luis Barrera, brother of American Hall of Fame thoroughbred racehorse trainer Laz Barrera, Summing is best known for his upset over U.S. Champion 3-Yr-Old Colt Pleasant Colony in the Belmont Stakes with George Martens aboard.
Summing was pensioned from study duties in September 2003 due to declining fertility[4] and stood at the farm until he died in his sleep of natural causes at 30 years old in October, 2008.