Partisanship in Congress in Two Neat Diagrams

Just look at this image from Vox which shows polarization in Congress from 1949 to the present. Political scientists Poole and Roosenthal and the two given credit for the research on Congressional polarization.  In fact if you know how to do multivariate regressions, they have a data set for every single Congress.  Below is there image (a little better than Vox). You can find a larger image and lots of others here.

I found the Vox diagram on the Facebook page for AP US Government teachers.