In the next month, on the day after he turned fifteen years old, Crocker began work in Boston as an apprentice in the printing-office of Samuel Turell Armstrong (afterwards mayor of Boston and acting governor of the Commonwealth), who also carried on a bookselling business.

At age 19 Crocker was made foreman of the printing-office, and at 22 was, with his fellow-apprentice Osmyn Brewster taken into partnership with Armstrong.

After 1825 the entire business was carried on under the name of Crocker & Brewster (although Mr. Armstrong continued a member of the firm until 1840).

In 1866, Dartmouth College conferred upon him an honorary degree of A. M. He died at his summer residence in Cohasset on July 19, 1887.

Crocker was a leader in the movement for building the Bunker Hill Monument and raised $40,000 for the fund.