Of the artists on the Billboard Top 100 this spring, we looked at the 50 that were most watched on YouTube in the United States between January 2016 and April 2017. Each map shows relative popularity in different parts of the country. If one part of a map is lighter, it doesn’t mean people there weren’t watching the artist’s videos; it just means fans were more likely to listen to a variety of other artists.     1. Future  2. Rihanna   3. Twenty One Pilots