Glennon Jamboretz began his advertising career in St. Louis with Gardner Advertising as manager of the Jack Daniel's account. After working at Leo Burnett's Chicago and New York offices, he returned to St. Louis and joined Stolz Advertising. Within four years he was president of the firm and later, as CEO, he changed the name to the Glennon Companies. Glennon did work for national firms like Robert Mondavi Winery, Nestle, Midas, McDonald's, Monsanto and Anheuser-Busch. He was president of the Ad Club of St. Louis and other trade organizations as well, and he dedicated much of his time to serving on boards of local civic organizations. Jamboretz later established Lafayette Partners, which specialized in public policy consultancy.