In the late 19th century, wealthy merchant Cyrus Gold was murdered, his body dumped in Slaughter Swamp. Due to the weird properties of the swamp, Gold was reborn years later as a strong and simple-minded monster. Since he rose from the swamp on a Monday, the monster was given the name Solomon Grundy after the nursery rhyme. Because of his simple-minded and violent nature, Grundy has often been involved in crime and destruction.
Grundy has been destroyed many times, and has risen again each time with different personality, ranging from a rampaging mindless monster to sinister fiend. Once he had a gentle, child-like personality and ended up befriending several different super-heroes.