She was owned and bred by Francis Morris of New York, foaled on Morris’s farm in Throgg’s Neck, New York. Her sire, Eclipse, and dam, Barbarity, were both imported. Morris bred the pair repeatedly producing several colts who accomplished little on the track but several award winning fillies. Track folks referred to the group of daughters as the “Barbarous Battalion” individually named Remoreseless, Relentless, Regardless, Merciless and Ruthless.
As a two-year old, Ruthless won the inaugural running of he Nursery Handicap, 1866, by six lengths. She carried 97 pounds for the 1-mile race and won $2,450. The New York Times commented that she finished the race “galloping along as she was at exercise”.
On June 4 the following year Ruthless raced in the Jersey Derby’s 1 ½ mile course finishing second, two lengths back, to her stablemate, Monday. Two weeks later on June 19 she won the first Belmont Stakes race at Jerome Park Racetrack.