The 1904 United States presidential election in Illinois took place on November 8, 1904. All contemporary 45 states were part of the 1904 United States presidential election. State voters chose 27 electors to the Electoral College, which selected the president and vice president.
Illinois was won by the Republican nominees, incumbent President Theodore Roosevelt of New York and his running mate Charles W. Fairbanks of Indiana. They defeated the Democratic nominees, former Chief Judge of New York Court of Appeals Alton B. Parker and his running mate, former US Senator Henry G. Davis of West Virginia. Roosevelt won the state by a wide margin of 28.34%.