Using a wide array of sources, The New York Times shows how the virus spread at a granular level. The foundation is a map with moving dots, and the piece takes you through movements based on cell phone data and air travel in concert with known coronavirus cases.
Your jaw might drop a few times as you go through it.
Back in March, NYT published a similar work for how the spread started in China. We were talking about washing hands and restaurants closing. Thinking back to then and seeing where we are now stings.