Secretariat first race was on July 4, 1972 and his last race was on October 28, 1973 spanning 16 months.

Secretariat (March 30, 1970 – October 4, 1989) was an American Thoroughbred racehorse who, in 1973, became the first Triple Crown winner in 25 years. His record-breaking win in the Belmont Stakes, where he left the field 31 lengths behind him, is widely regarded as one of the greatest races of all time.

For his first start on July 4, 1972 at Aqueduct Racetrack, Secretariat was made the lukewarm favorite at 3–1. At the start, a horse named Quebec cut in front of the field, causing a chain reaction that resulted in Secretariat being bumped hard. According to jockey Paul Feliciano, he would have fallen if he hadn't been so strong. Secretariat recovered but only managed to finished fourth, beaten by only ​11⁄4 lengths. In many of his subsequent races, Secretariat hung back at the start, which Laurin later attributed to the bumping he received in his debut.

Secretariat's last race was against older horses in the Canadian International Stakes over one and five-eighths miles on the turf at Woodbine Racetrack in Toronto, Ontario, Canada on October 28, 1973. On the backstretch, Secretariat made his move and forged to the lead. "Snorting steam in the raw twilight", he rounded the far turn with a 12-length lead before gearing down in the final furlong, ultimately winning by ​61⁄2 lengths. That was his 16th win out of 31 races.

More Info: en.wikipedia.org