Born in St. Louis, Missouri, Conn McCreary began his professional career in 1937 and got his first win the following year at Chicago's Arlington Park.

In 1941, he earned the first of his many important wins when he rode "Our Boots" to victory in the Blue Grass Stakes at Keeneland Race Course over the heavily favored Whirlaway.

In the ensuing Kentucky Derby and Preakness Stakes, McCreary and "Our Boots" finished eighth and third respectively to winner Whirlaway who went on to win the U.S.

Among the top quality horses he rode were four Hall of Fame inductees, Devil Diver, Armed, Bric A Bac, and Stymie.

He then worked as a publicity agent for Hialeah and Calder racetracks before becoming the manager of Golden Hawk Farm in Ocala, Florida where he was employed until the time of his death in 1979.