40 years since Amii Stewart's disco version of 'Knock on Wood' topped pop chart

It's been 40 years since Amii Stewart's disco version of "Knock on Wood" reached No. 1 on the Billboard pop chart.

Eddie Floyd and Steve Cropper had written the song more than a decade earlier at the Lorraine Motel in Memphis, Tenn. Cropper has said in interviews that there were storms that night, which inspired the line about thunder and lightning.

The song has been covered by many artists since, including Otis Redding and Carla Thomas, David Bowie and yes — Amii Stewart.