A Political Map of the United States Congress, 1789-2011
By Kunal Jasty



After 112 Congresses the political map of the United States has changed more than you’d think. Here’s a guide where the Congressional delegations from each state — senators and congressman — lay along the liberal-conservative spectrum over the past 225 years.

A quick note. We didn’t include trends in social liberalism and conservatism — slavery, civil rights, abortion, same-sex marriage — which tend to change their meaning over time (Would you call a Southern, segregationist, FDR voter a liberal or a conservative using our modern definitions?) Instead, we placed populist, fiscally liberal delegations on the left and fiscally conservative delegations on the right.

We used the DW-NOMINATE dataset from Keith Poole and Howard Rosenthal, which you can read about here. Each state score was calculated by averaging the DW-NOMINATE scores of every senator and representative from that state. (Please comment below if you have any additional comments about our methodology.)

Drag the top bar or press the play button to see the continual change of political map of the United States. Take a look at the solidly Democratic South after Reconstruction, and the switch that occurs in the mid 20th century. Wendy Davis and the Democrats were hopeful that the blue South could rise again. Will it? And what other trends do you notice?

  • Kunal

    Probably should have, same thing with Maine + Massachusetts