Grant obtained A.B. and A.M. degrees from Williams College in 1846 and graduated from the College of Physicians and Surgeons in 1851. In 1852, he worked as a surgeon in Panama during the height of the California Gold Rush (when hordes of prospectors traveled across the isthmus on their way to the gold fields by sea) and organized the American Hospital the following year. While there, he also edited the "Panama Herald". He then returned to practice medicine in his hometown of Newark. In 1854, he was part of a special commission set up to fight the cholera epidemic in the city.