He also cofounded the Choate Rosemary Hall college, a private boarding school in Wallingford, Connecticut.

He was in private practice in Danvers, Massachusetts from 1855 to 1857, then in Salem until 1865, and then in New York City from 1865 to 1878.

[2] On March 14, 1878, Choate was nominated by President Rutherford B. Hayes to a seat on the United States District Court for the Southern District of New York vacated by Judge Samuel Blatchford.

Choate was confirmed by the United States Senate on March 25, 1878, and received his commission the same day.

[2] Following his resignation from the federal bench, Choate resumed private practice in New York City from 1881 to 1920.