Federalist, a name in the United States for a supporter of the Union and its integrity as such; a party which was formed in 1788, but dissolved in 1820; has been since applied to a supporter of the integrity of the Union against the South in the late Civil War.
Definition taken from The Nuttall Encyclopædia, edited by the Reverend James Wood (1907)
Federal Government * Federation, The Champs-de-Mars