He served in both houses of the state legislature and represented Pennsylvania in the United States. House from 1793 until 1795 and from 1799 to 1812. Smilie was a prominent Jeffersonian, and was identified with the ""Quid" branch of the party. In 1806-1807, during the debates over the abolition of the slave trade, Smilie was among the most outspoken against the evils of the slave trade.
He argued that slaves illegally imported after 1808 should be freed, and that slave smugglers deserved the death penalty.
Neither provision was adopted. Smilie was born in Ireland and immigrated around 1760, settling first in Lancaster County.
He moved to Fayette in 1780. He was elected to the Thirteenth Congress in 1812 but died before it opened.
He died in Washington, District of Columbia, aged 71, and is buried in the Congressional Cemetery there.