Where was the Republican Party of the United States founded?

Founded in the Northern states in 1854 by anti-slavery activists, modernizers, ex-Whigs, and ex-Free Soilers. The main cause was opposition to the Kansas–Nebraska Act, which repealed the Missouri Compromise by which slavery was kept out of Kansas. The Northern Republicans saw the expansion of slavery as a great evil. The first public meeting where the name "Republican" was suggested for a new anti-slavery party was held on March 20, 1854 in a schoolhouse in Ripon, Wisconsin. The name was partly chosen to pay homage to Thomas Jefferson's Republican Party.

The first official party convention was held on July 6, 1854, in Jackson, Michigan. By 1858, the Republicans dominated nearly all Northern states. The Republican Party first came to power in 1860 with the election of Abraham Lincoln to the Presidency