Resolved: That the Constitution confers upon Congress sovereign powers over the Territories of the United States for their government; and that in the exercise of this power, it is both the right and the imperative duty of Congress to prohibit in the Territories those twin relics of barbarism - Polygamy, and Slavery.
Horace Greeley, one of the founders of the Republican party
The year is 1856. The issue of slavery divides the nation and threatens to tear it apart. As the country expands, tensions between slave-states and free states flare. Opponents of slavery are determined to halt the spread of the abominable practice into the new territories, eventually ending it altogether. A new political party is formed to meet this ambitious goal, holding its first convention in Philadelphia, the City of Brotherly Love. Philadelphia has gone on to host the convention a total of six times, most recently in 2000.
The earliest representation of the Republican party as an elephant, appeared in an 1874 Harper's Weekly cartoon by Thomas Nast
A cornerstone of modern Republican political philosophy is limited government, but in 1856, it was northern Republicans calling for the exercise of federal authority to halt the expansion of slavery, while southern Democrats defended their "peculiar institution" on the principle of state's rights.
The evolution of our two major political parties into the very different entitites they are today is all part of the ongoing story of the USA. But like the history of our nation itself, the history of the GOP starts in Philadelphia.