Jonathan Trumbull Sr. combined a mercantile career with more than fifty years in Connecticut public life. Elected to the General Assembly in 1733, he held legislative, judicial and militia responsibilities while managing a trading business in Lebanon. Supply contracts brought opportunities, but debts threatened his finances. His standing also rested on administrative experience.

He opposed imperial measures such as the Stamp Act and became deputy governor in 1766, also serving as chief justice. When Governor William Pitkin died in 1769, Trumbull succeeded him. Connecticut's charter allowed colonists to choose their governor, giving him a position different from that of royal appointees elsewhere. He supported resistance to Britain and remained in office through independence, becoming the state's first governor without an abrupt change of executive leadership.

During the Revolutionary War, Trumbull worked closely with George Washington to procure troops, food, clothing, ammunition and transport. His former store in Lebanon became a war office and meeting place for the Council of Safety. The legislature gave him unusual authority to deal with urgent military needs, but he still had to negotiate resources with towns, suppliers and fellow officials. Connecticut's contribution earned its reputation as the Provisions State.

Trumbull also defended Connecticut's controversial western land claims, including its settlements in the Susquehanna region, which brought conflict with Pennsylvania. He supported the continuation of charter government after independence rather than an immediate constitutional reconstruction. Retiring in 1784, he left a record of wartime coordination that became central to state memory. His celebrated relationship with Washington later generated stories about the nickname Brother Jonathan; these traditions are less securely documented than the work of supplying an army through years of shortages.