ATCO Records was founded in 1955 as a division of Atlantic Records. It was intended as a home for acts that did not fit the format of Atlantic, which at the time was only releasing blues, jazz, and R&B/soul. The Atco name is simply an abbreviation of Atlantic Corporation.
Atlantic deemphasized Atco in the mid-1970s, using the label mostly for releases by hard rock acts and some British and European bands. The label is now operating as a division of Warner Music Group.