Polarization is at historic highs at the national level. Everyone knows that.

But, closer to the ground, polarization is growing too. As WaPo's Dan Balz explains in a terrific piece today,  partisanship at the state legislative level is also soaring -- with a single party controlling all levers of state government in three quarters of the 50 states.

The chart below -- put together by the talented Kennedy Elliott -- shows how party control of each state has changed over time.