Cornerstone is the ninth studio album by the American rock band Styx, released in 1979. Styx's third straight multi-platinum selling album, Cornerstone was Styx's first album to earn a Grammy nomination, which was for Best Rock Performance by a Duo or Group. Like the four previous Styx albums, the band produced the album themselves. Styx recorded the album at Pumpkin Studios in Oak Lawn, Illinois.