5. We identify ourselves as Democrats and Republicans.
Before 1854, you might have been a Whig. Or a Free Soiler. But that year the Republican Party was founded by anti-slavery activists and refugees from other political parties to fight the iron grip of powerful southern Democrats.
As the name of their party suggests, these activists believed that the republic's interests should take precedence over the states'. In the years before the war, many northern Democrats defected to join the new party — and, in 1860, to elect Abraham Lincoln as the first Republican president — while southern Democrats led the march to secession.
The Democratic and Republican parties both survived the war and have held their spots as the dominant U.S. political parties ever since. The "Solid South," as it was known, protected the interests of agrarian Southern whites and consistently elected Democrats to Congress from Reconstruction through the early 1960s, when the national Democratic Party's support of the civil rights movement allowed the Republican Party to begin making new political inroads below the Mason-Dixon Line.
Within a few years, North and South swapped party hats. Conservative southerners grew disenchanted with the Democratic Party's increasingly progressive platforms. Republicans capitalized on this with their "Southern Strategy," an organized plan to make headway there on a socially conservative, states' rights platform. In reverse, historically Republican strongholds in the Northeast began voting Democrat, establishing the pattern of red and blue that we see on election-night maps today.