Sam's father died when he was young, and as the oldest sibling he felt responsible for supporting the family. Giving up college, he followed in his father's footsteps as a coal miner. When Sam was trapped with a co-worker in a collapsing mine, the stress of attempting to escape triggered his latent mutant power, enabling him to blast them both free. Professor Xavier subsequently invited him to join the New Mutants as Cannonball.