Thomas Mackean, an American jurist, and a signer of the Declaration of Independence, born in Chester co., Pa., March 19, 1734, died in Philadelphia, June 24, 1817. In 1757 he was admitted to the bar, and in 1762 was elected a member of the Pennsylvania assembly, to which he was annually returned for the next 17 years. In 1765 he attended the general congress of the colonies at New York, and formed one of the committee who framed the address to the British house of commons; and in the same year he was appointed judge of the court of common pleas for New Castle county. In September, 1774, he took his seat in the first continental congress, as a delegate from the lower counties in Delaware. He was a member of congress, of which he was elected president in 1781, until February, 1783, being the only member who served without interruption during the whole revolutionary period. In 1777, while still a representative in congress from Delaware, he was appointed chief justice of Pennsylvania, and in the same year he also officiated as president of the state of Delaware, for which he drew up a constitution. He retired from the bench in 1799, on being elected governor of the state. His administration lasted until 1808, when he withdrew from public life.

As a jurist he held a high position for integrity, impartiality, and learning. In politics he was one of the leaders of the republican party, the ascendancy of which in Pennsylvania was in no small degree owing to his exertions.