Starting on April 18th, protests began in Baltimore following the coma of Freddie Gray, whom had suffered a spinal injury following an arrest. These protests grew worse following his death before reaching a boiling point on May 1st as the six cops involved were indicted. The protests turned to riots, with the rioters setting buildings on fire and looted local businesses.
This ties into American history through the riots that broke out in the Union states during the Civil War. During the riots in the Union, however, the people were protesting all the young men being shipped off to their deaths due to the draft. Both, however, can relate to each other.