In addition to a long career practicing law in Jamestown, he served as a member of the New York State Assembly, district attorney and judge of Chautauqua County, and a member of the United States House of Representatives.

After attaining admission to the bar in 1819, he practiced continually for 60 years, and was still active when he died at age 86.

[2] In addition to practicing law, Hazeltine was also interested in several Jamestown-area businesses, including serving as a director of the Chautauqua County Bank.

[6] He was also an opponent of slavery, and opposed motions to ban anti-slavery petitions from being received by the House.

[2] When the Republican Party was founded in the mid-1850s, Hazeltine became an early member, and he served as judge of Chautauqua County from 1859 to 1863.

[2][8] During the American Civil War, he was appointed a state commissioner for overseeing the Union Army draft in Chautauqua County.

[2][10] Hazeltine served as United States Commissioner for the courts of the Northern District of New York from 1873 until his death.

[3][12] Lewis was a physician, Abner Jr. became an attorney, and Mary was the wife of Jamestown merchant De Forest Weld.