Also a Jeffersonian coinage. A fellow-state.
1798. This commonwealth does therefore call on its co-States for an expression of their sentiments . The rights and liberties of their co-States will be exposed to no dangers.Thomas Jefferson, Resolutions relative to the Alien and Sedition laws: Works, ix. 471 (1859).
1841. There is meaning in those words, Empire State, when used among co-estates, more than meets the ear.John Q. Adams in the House of Repr., Sept. 4: Cong. Globe, p. 433, App.