Kelso raced in top competion from his 3 year old thru 8 year old seasons winning such prestigious races as the Jockey Club Gold Cup (5 consecutive years when it was still a 2 mile race), Hawthorne Gold Cup, Met Mile, Suburban Hcp. (2 wins and 3 seconds), Brooklyn Hcp. (becoming the third horse ever to win the Handicap Triple), Woodward Stakes (3 wins and a second), Washington DC International (1 win and 3 seconds back when this was a really big race).
Kelso was a homebred foal for Mrs. Richard (Allaire) duPont and raced for her Bohemia Stables his entire career. He was born on April 4, 1957, at Claiborne Farm and was a rather small colt with little to distinguish him from the other 10,792 foals born that year. Because he was a late foal and a bit small, Kelso got off to a slow start at the track and only raced 3 times as a 2 year old in September at Atlantic City Race Course although he did win at first asking.
Kelso also got a late start for his 3 year old season due to a change in trainers to Carl Hanford who handled him for the remainder of his career. Because of this, he missed out all the Triple Crown races. His first two starts were in allowance events at Monmouth and Aqueduct where he won going away in double digit lengths. Kelso was shipped to Arlington Park for his stakes debut in the Arlington Classic but he finished up the track. This loss was later attibuted to tender feet and an overly hard track and was to be his only defeat of the year. He came back to Monmouth and won his first stakes race, the Choice Stakes going away. The rest of the year Kelso raced in handicap conditions beating the older horses and setting two track records and and American records. Kelso was acclaimed champion 3-year-old and Horse of the Year for his achievements.
A wrenched stifle delayed Kelso's return to the track in 1961 until May but he came back running to win an allowance and then the Metropolitan Handicap under 130 pounds. He followed this up with a second by a head in the Whitney where he was awarded first via a disqualification then back to back wins in the Suburban and the Brooklyn Handicaps under 133 and 136 pounds to become only the third horse ever to win the Handicap Triple. He finished out the year with devastating victories in the Woodward and the Jockey Club Gold Cup Stakes and a second place in his first ever grass race, the Washington DC International. Kelso came out of that race with an injured hock and went to the farm to recover. He was voted champion handicap horse and Horse of the Year for the second straight year.
In 1962 a virus set his training back and Kelso lost his first start, the Metropolitan. He won an easy allowance event next out but still didn't seem quite himself as he followed it up with a second in the Suburban and then the Monmouth Handicap. He raced in a couple of allowances to get his feet under him and then finished out the year in style winning the Woodward, Jockey Club Gold Cup for the third time, and the Governor's Plate along with second place finishes in the Man O'War and the Washington DC International. Kelso closed out the year as racing's fifth equine millionare and was again voted champion handicap horse and Horse of the Year.
Because he was going so well now, Kelso didn't take off the winter but went down to Florida to start his 1963 season. There he won the Seminole at Hialeah and the Gulfstream Park Handicap before heading north. He then reeled off seven consecutive major stakes wins carrying up to 134 pounds. He closed out the year with another second in the Washington DC International which brought his seasonal earnings to over half a million. Kelso was again voted champion handicap horse and Horse of the Year.