[1] He was admitted to the bar and entered private practice in Augusta, District of Maine (then part of Massachusetts) from 1815 to 1817.

[2] He was elected to the United States Senate from Maine and served from March 4, 1829, to January 1, 1835, when he resigned.

[2] During his time in the Senate, Sprague became a prominent campaigner against President Andrew Jackson's controversial policy of Indian removal, whereby Indians in the Southern states were to be forcibly relocated to West of the Mississippi River.

Sprague argued that the policy was corrupt as it largely relied on bribes for support, and he also attacked the plan for its immorality and lack of humanity, claiming that the Indians would receive no assistance in starting new lives in an alien environment.

[1] He was confirmed by the United States Senate on July 16, 1841, and received his commission the same day.