This is a visualization choropleth I put together of Covid-19 infections for each county over time. It's based on the NY Times data set and I built the images in Python based off a very good, if ancient, tutorial I found at FlowingData.
Edit: Updated through Apr. 13 data, and also made the original larger. Not sure if that matters for this web page or not.
This image is licensed under the Creative Commons Attribution-NonCommercial 4.0 International license. I would appreciate attribution if you care to use it!