David Sparks created this video that uses blue and red to show shifts in voting patterns (Democratic vs. Republican) in all the presidential elections since 1920:

Sparks points out several interesting patterns that emerge:

1. Voting in urban areas often differs from other parts of their states (for example, Salt Lake City stands out from the rest of Utah, as did San Francisco from the rest of California in 1980).

2. We can see the South swing from solidly Democratic to predictably Republican (as Sparks highlights, the 1924 and 2004 maps are nearly inverted).

3. Despite clear patterns (such as the South going Republican, a coasts vs. interior voting split), we often see fairly drastic shifts between one presidential election and the next, as well as temporary disruptions to the overall trend (for instance, the reliably Republican South went Democratic in 1980).

As Sparks puts,

More broadly, this video is a reminder that what constitutes “politics as usual” is always in flux, shifting sometimes abruptly. The landscape of American politics is constantly evolving,  as members of the two great parties battle for electoral supremacy.

He also has a thorough explanation of his methodology for creating the map, if you’re interested.