The Republican Party evolved from the political factions that opposed Alexander Hamilton's fiscal policies; these factions are known variously as the Anti-Administration "Party" or the Anti-Federalists. In the mid-1790s, Thomas Jefferson and James Madison organized these factions into a party and helped define its ideology in favor of yeomen farmers, strict construction of the Constitution, and a weaker federal government.
In 1796, the Republicans made their first bid for the Presidency with Jefferson as their Presidential candidate and Aaron Burr as the Vice Presidential candidate. Due to the vagaries of the pre-12th Amendment electoral process, even though Jefferson failed to become President, he did become Vice President. For the next four years, Jefferson was able to use his position as President of the Senate as a platform to protest the policies of the Adams administration.
The breakthrough occurred in 1800. In what is sometimes referred to as the "Revolution of 1800", the Republicans took control of the Presidency and both houses of Congress, beginning a quarter century of control of those institutions. The opposition Federalists, suffering from a lack of leadership after the death of Hamilton and the retirement of Adams, slowly declined over the next fifteen years until the Hartford Convention utterly destroyed them as a political force.
This left the Republican Party as the sole party in the United States government, ushering in a brief hiatus from the standard political debates known as the Era of Good Feeling. When President James Monroe retired from the Presidency, the fight to succeed him in the 1824 presidential election splintered the Republican Party into numerous factions. The strongest of these factions supported Andrew Jackson and would evolve into the Democratic Party. The other factions would form an opposition which evolved into the National Republicans, and then the Whigs.
Republicans had a good hold on Chicago for many years. Chicago had a total of 10 Republicans that Served as Mayor begining in 1857 with Mayor John Wentworth who held 2 terms.
"Long" John Wentworth 1st term: March 3, 1857; 2nd term: March 6, 1860-1st term: 1857-1858; 2nd term: 1860-1861
John Charles Haines 1st term: March 2, 1858; 2nd term: March 1, 1859-1st term: 1858-1859; 2nd term: 1859-1860
Julian Sidney Rumsey April 1, 1861; Term of office: 1837-1838
John Blake Rice 1st term: April 18, 1865; 2nd term: April 16, 1867-1st term: 1865-1867; 2nd term: 1867-1869
Monroe Heath 1st term: July 12, 1876; 2nd term: April 3, 1877; 1st term: July 24, 1876; 2nd term: April 30, 1879-1st term: 1876-1877; 2nd term: 1877-1879
John A. Roche April 5, 1887; Term of office: 1887-1889
Hempstead Washburne April 7, 1891 Term of office: 1891-1893
George Bell Swift 1st term: November 6, 1893; 2nd term: April 2, 1895-1st term: 1893; 2nd term: 1895-1897
Fred A. Busse April 2, 1907; Terms of office: 1907-1911
William Hale "Big Bill" Thompson 1st term: February 23, 1915; 2nd term: February 25, 1919; 3rd term: February 24, 1931-1st term: 1915-1919; 2nd term: 1919-1923; 3rd term: 1927-1931
Several Republicans have attempted to run for Mayoral Office and were defeated ever since they made their first debute April 15, 1862 when Francis Cornwall Sherman defeated Charles N. Holden on his 2nd term. But, the last Republican that won a victory in the Mayoral office was William Hale "Big Bill" Thompson in February 23, 1915 and held his office for 8 years 1st term: 1915-1919-2nd term: 1919-1923; he took a four year break in which Democrat, William Emmett Dever held office before his return in 1927, which added 4 more years, which finally came to an end in 1931, after Democrat, Anton Joseph Cermak beaten him.