Greenough, born in Boston, was the first American sculptor to study in Italy. He traveled to Rome in 1825 and settled in Florence, where he trained with Lorenzo Bartolini, who encouraged his students to study human anatomy and to sketch from live models. In classical mythology, Castor and Pollux were twins. Castor was killed in battle, but the god Zeus allowed them to spend alternate days on earth, greeting each other in passing. In this work, Greenough clearly referred to ancient art. He represented the legend in low relief, arranging the figures and horses into a perfectly balanced oval; he also carved the wooden pedestal.