Thomas McKean was born in Pennsylvania in 1734 to William McKean and Letitia Finney. His father was a tavern-keeper in New London and both his parents were Irish-born who came to Pennsylvania as children from Ballymoney, County Antrim, Ireland.

A few days after McKean cast his vote, he left Congress to serve as colonel in command of the Fourth Battalion of the Pennsylvania Associators, a militia unit created by Benjamin Franklin in 1747. They joined Washington’s defense of New York City at Perth Amboy, New Jersey. Being away, he was not available when most of the signers placed their signatures on the Declaration of Independence on August 2, 1776. Since his signature did not appear on the printed copy that was authenticated on January 17, 1777, it is assumed that he signed after that date, possibly as late as 1781.

McKean’s education began at the Reverend Francis Allison’s New London Academy. At the age of sixteen, he went to New Castle, Delaware to begin the study of law under his cousin, David Finney. In 1755 he was admitted to the Bar of the Lower Counties, as Delaware was then known, and likewise in the Province of Pennsylvania the following year. In 1756 he was appointed deputy attorney general for Sussex County. From the 1762/63 session through the 1775/76 session, he was a member of the General Assembly of the Lower Counties, serving as its Speaker in 1772/73. From July 1765, he also served as a judge of the Court of Common Pleas and began service as the customs collector at New Castle in 1771. In November 1765 his Court of Common Pleas became the first such court in the colonies to establish a rule that all the proceedings of the court be recorded on un-stamped paper. In 1768, McKean was elected to the revived American Philosophical Society.

Mary Borden was his first wife. They married in 1763, and lived at 22 The Strand in New Castle, Delaware. They had six children: Joseph, Robert, Elizabeth, Letitia, Mary, and Anne. Mary Borden McKean died in 1773 and is buried at Immanuel Episcopal Church in New Castle. Letitia McKean married Dr. George Buchanan and was the mother of CS Admiral Franklin Buchanan.

Sarah Armitage was McKean’s second wife. They married in 1774, lived at the northeast corner of 3rd and Pine Streets in Philadelphia, Pennsylvania, and had four children, Sarah, Thomas, Sophia, and Maria. They were members of the New Castle Presbyterian Church in New Castle and the First Presbyterian Church in Philadelphia. McKean’s daughter Sarah married Spanish diplomat Carlos Martínez de Irujo, 1st Marquis of Casa Irujo; their son, Carlos Martínez de Irujo y McKean, would later become Prime Minister of Spain.

In spite of his primary residence in Philadelphia, McKean remained the effective leader for American independence in Delaware. Along with George Read and Caesar Rodney, he was one of Delaware’s delegates to the First Continental Congress in 1774 and the Second Continental Congress in 1775 and 1776.

Being an outspoken advocate of independence, McKean’s was a key voice in persuading others to vote for a split with Great Britain. When Congress began debating a resolution of independence in June 1776, Caesar Rodney was absent. George Read was against independence, which meant that the Delaware delegation was split between McKean and Read and therefore could not vote in favor of independence. McKean requested that the absent Rodney ride all night from Dover to break the tie. After the vote in favor of independence on July 2, McKean participated in the debate over the wording of the official Declaration of Independence, which was approved on July 4.

In a conservative reaction against the advocates of American independence, the 1776/77 Delaware General Assembly did not reelect either McKean or Caesar Rodney to the Continental Congress in October 1776. However, the British occupation following the Battle of Brandywine swung opinions enough that McKean was returned to Congress in October 1777 by the 1777/78 Delaware General Assembly. During this time, he was constantly pursued by British forces. Over the course of the following years, he was forced to relocate his family five times.

Meanwhile, McKean led the effort in the General Assembly of Delaware to declare its separation from the British government, which it did on June 15, 1776. Then, in August, he was elected to the special convention to draft a new state constitution. Upon hearing of it, McKean made the long ride to Dover, Delaware from Philadelphia in a single day, went to a room in an Inn, and that night, virtually by himself, drafted the document. It was adopted September 20, 1776. The Delaware Constitution of 1776 became the first state constitution to be produced after the Declaration of Independence.

Pennsylvania elections were held in October as well. The Pennsylvania Supreme Executive Council was created in 1776 and counsellors were popularly elected for three-year terms. A joint ballot of the Pennsylvania General Assembly and the council chose the president from among the twelve counsellors for a one-year term. The chief justice of the Pennsylvania Supreme Court was also selected by the General Assembly and Council for the life of the person appointed.

McKean was then elected to Delaware’s first House of Assembly for both the 1776/77 and 1778/79 sessions, succeeding John McKinly as Speaker on February 12, 1777, when McKinly became President of Delaware. Shortly after President McKinly’s capture and imprisonment, McKean served as the President of Delaware for a month, from September 22, 1777, to October 20, 1777. That was the time needed for the rightful successor to John McKinly, the Speaker of the legislative council, George Read, to return from the Continental Congress in Philadelphia and assume the duties.

McKean started his long tenure as Chief Justice of Pennsylvania on July 28, 1777, and served in that capacity until 1799. There he largely set the rules of justice for revolutionary Pennsylvania. According to biographer John Coleman, “only the historiographical difficulty of reviewing court records and other scattered documents prevents recognition that McKean, rather than John Marshall, did more than anyone else to establish an independent judiciary in the United States. As chief justice under a Pennsylvania constitution he considered flawed, he assumed it the right of the court to strike down legislative acts it deemed unconstitutional, preceding by ten years the U.S. Supreme Court’s establishment of the doctrine of judicial review. He augmented the rights of defendants and sought penal reform, but on the other hand was slow to recognize expansion of the legal rights of women and the processes in the state’s gradual elimination of slavery.”

Later, he served continuously until February 1, 1783. McKean helped draft the Articles of Confederation and voted for their adoption on March 1, 1781. When poor health caused Samuel Huntington, to resign as President of Congress in July 1781, McKean was elected as his successor. He served from July 10, 1781, until November 4, 1781. The President of Congress was a mostly ceremonial position with no real authority, but the office did require McKean to handle a good deal of correspondence and sign official documents. During his time in office, Lord Cornwallis’s British army surrendered at Yorktown, effectively ending the war.

McKean was a member of the Pennsylvania Society of the Cincinnati in 1785 and was subsequently its vice-president. Princeton College gave him the degree of L.L.D. in 1781, Dartmouth College presented the same honor in 1782, and the University of Pennsylvania gave him the degree of A.M. in 1763 and L.L.D. in 1785. With Professor John Wilson he published “Commentaries on the Constitution of the United States” in 1790.

While Chief Justice of Pennsylvania, McKean played a role in the Whiskey Rebellion. On August 2, 1794, he took part in a conference on the rebellion. In attendance was Washington, his Cabinet, the Governor of Pennsylvania, and other officials. President Washington interpreted the rebellion to be a grave threat could mean “an end to our Constitution and laws.” Washington advocated “the most spirited and firm measure” but held back on what that meant. McKean argued that the matter should be left up to the courts, not the military, to prosecute and punish the rebels. Alexander Hamilton naturally, insisted upon the “propriety of an immediate resort to Military force.”

He was a member of the convention of Pennsylvania, which ratified the Constitution of the United States. In the Pennsylvania State Constitutional Convention of 1789/90, he argued for a strong executive and was himself a Federalist. Nevertheless, in 1796, dissatisfied with Federalist domestic policies and compromises with Great Britain, he became an outspoken Jeffersonian Republican or Democratic-Republican.

McKean was elected Governor of Pennsylvania and served three terms from December 17, 1799, until December 20, 1808. In 1799 he defeated the Federalist Party nominee, James Ross, and again more easily in 1802. At first, McKean ousted Federalists from state government positions and so he has been called the father of the spoils system. However, in seeking a third term in 1805, McKean was at odds with factions of his own Democratic-Republican Party, and the Pennsylvania General Assembly instead nominated Speaker Simon Snyder for governor. McKean then forged an alliance with Federalists, called “the Quids,” and defeated Snyder. Afterwards, he began removing Jeffersonians from state positions.

The governor’s beliefs in stronger executive and judicial powers were bitterly denounced by the influential Aurora newspaper publisher, William P. Duane, and the Philadelphia populist, Dr. Michael Leib. After they led public attacks calling for his impeachment, McKean filed a partially successful libel suit against Duane in 1805. The Pennsylvania House of Representatives impeached the governor in 1807, but his friends prevented a trial for the rest of his term, and the matter was dropped.

McKean died in Philadelphia and was buried in the First Presbyterian Church Cemetery there. In 1843, his body was moved to Laurel Hill Cemetery.