UMW General coal strike (1922)
The 1922 UMW Miner strike or The Big Coal Strike was a nationwide general strike of miners in the US and Canada after the United Mine Worker's (UMW) trade union contract expired on March 31, 1922. The strike decision was ordered March 22, to start effective April 1.
Source: Wikipedia — UMW General coal strike (1922) (CC BY-SA 4.0)