McCann Erickson is an advertising agency on Madison Avenue in New York City. They are one of SCDP's primary competitors.
Because of the impending sale of Puttnam, Powell, and Lowe, which owned Sterling Cooper Advertising Agency, to McCann, Lane Pryce was convinced to free Don Draper, Bertram Cooper, and Roger Sterling from their employment contracts to start Sterling Cooper Draper Pryce. ("Shut the Door. Have a Seat")