[1][a] Leonard received his Master of Arts degree from Harvard in 1751.

[2] He began the study of law while serving as Bristol County's register of probate, an office he held from 1749 to 1783.

[1] From 1764 to 1766, Leonard served as a member of the Massachusetts Provincial Assembly.

[1] From 1784 to 1790, Leonard was judge of the probate court in Bristol County.

[1] In 1788, Leonard was elected to the United States House of Representatives as a Pro-Administration candidate.