Thomas McKean Thompson McKennan was born in 1794 in New Castle, Delaware, and graduated from Washington College (later Washington and Jefferson College) in Pennsylvania. McKennan then worked as a tutor in ancient languages, studied law, and was admitted to the bar in 1814.

From 1815 to 1817, McKennan served as attorney general of Washington County, Pennsylvania, before becoming a member of Washington’s town council from 1818 to 1831. In 1830, McKennan was elected to the U.S. House of Representatives, where he served three terms, from 1831 to 1839, and part of fourth term from 1842 to 1843.

When Millard Fillmore assumed the presidency in 1850, he tapped McKennan as secretary of the Interior Department. McKennan served only eleven days before he resigned his duties due to illness. Little is known about Thomas McKennan’s life from his resignation until his death in 1852.