Thomas McKean was born on March 19, 1734, in New London Township, Pennsylvania, the son of William McKean and Letitia Finney McKean. His parents were Scots-Irish Presbyterians living in a farming community near the Delaware border. The household emphasized religion, discipline, literacy, and advancement through education. McKean studied at the academy of the Reverend Francis Allison in New London, one of the colonies’ most respected schools. He learned Latin, mathematics, logic, rhetoric, and moral philosophy alongside several future political leaders. The school’s Presbyterian discipline emphasized careful argument, moral responsibility, and preparation for useful public service. He then read law under David Finney in New Castle, Delaware. Admitted to the Delaware bar in 1754, McKean also gained admission in Pennsylvania and New Jersey. Practicing across colonial boundaries taught him to navigate differing statutes, courts, and political cultures. His energetic temperament and formidable memory helped him rise rapidly. He married Mary Borden in 1763 and began a family. After her death, he married Sarah Armitage. McKean’s legal practice, property, and family obligations anchored him in both Delaware and Pennsylvania, a dual connection that shaped his unusual political career. Before signing the Declaration and serving as governor and chief justice, McKean had been shaped by Scots-Irish Presbyterian culture, rigorous academy education, legal apprenticeship, multicolonial practice, marriage, and early officeholding. He was not a gentleman of leisure; professional work created his standing. The habit of operating across jurisdictional lines later made him especially useful in continental politics, while his forceful personality—already visible at the bar—made him both effective and contentious.