The Gilded Age is generally believed to have taken place between the years 1870 and 1900. The term was originally coined by Mark Twain, who was one of the primary critics of the periods upper-class business elite.
Politics were very much divided into two camps - Republican and Democrat, but the divisions between the two parties were almost always along old Civil War lines. Republicans, the party of Lincoln, almost always won the northern states, where Union veterans and industrialists in favor of high tariffs helped them carry those states. Blacks also nearly always voted Republican in homage to Lincoln.
Democrats, who glorified the Confederate cause and played on the anti-Reconstruction views of racist whites and disaffected southerners. A group of Republicans, called the Mugwumps, abandon the Republican party in 1884 and helped elect Grover Cleveland as a way to protest Republican corruption.