On the advice of Irish-born trainer Tom Barry, Celtic Ash was purchased by Boston, Massachusetts banker Joseph E. O'Connell, who imported him to the United States to race for his Green Dunes Farm.
He was not entered in the Kentucky Derby but won two minor races at Laurel Park Racecourse, in one of which he set a new track record time for one mile.
After the Jersey Derby, Hartack accepted trainer Tom Barry's offer to ride Celtic Ash again in the upcoming Belmont Stakes.
The day prior to the Belmont Stakes, betting favorite Bally Ache came up lame and was withdrawn from the 1½ mile third leg of the Triple Crown.
On June 11, 1960, O'Connell was in a Brighton, Massachusetts, hospital and watched on television as Hartack brought his colt from last place to overtake Venetian Way in the stretch, then pull away to win easily by five and a half lengths.