The Third Party System was a period in the history of political parties in the United States from the 1850s until the 1890s, which featured profound developments in issues of American nationalism, modernization, and race. This period was marked by the American Civil War (1861–1865), the Emancipation Proclamation and the end of slavery in the United States, followed by the Reconstruction era and the Gilded Age.
It was dominated by the new Republican Party, which claimed success in saving the Union, abolishing slavery and enfranchising the freedmen, while adopting many Whig-style modernization programs such as national banks, railroads, high tariffs, homesteads, social spending (such as on greater Civil War veteran pension funding), and aid to land grant colleges. While most elections from 1876 through 1892 were extremely close, the opposition Democrats won only the 1884 and 1892 presidential elections (the Democrats also won the popular vote in the 1876 and 1888 presidential elections, but lost the electoral college vote), though from 1875 to 1895 the party usually controlled the United States House of Representatives and controlled the United States Senate from 1879 to 1881 and 1893 to 1895. Indeed, scholarly work and electoral evidence emphasizes that after the 1876 election the South's former slave centers, which before the emancipation of Republican-voting African Americans was electorally dominated by wealthy slave owners who made up the southern base of Whigs, Know Nothings and Constitutional Unionists, began realigning into the Democratic Party due to the end of the now unpopular Reconstruction efforts; this new electoral base for the Democrats would finish realigning around 1904.