It happened in the early 1950s. From the book October 1964:
Gussie Busch was stunned to find that the team he had just purchased was all white. Since Budweiser, its executives believed, sold more beer to black people than any other beer company in the country, Busch was nervous for economic reasons about owning a lily-white team. He could easily visualize a black boycott of his beer, and, to his credit, he also thought it was simply morally wrong to exclude blacks. That first year he visited the team in spring training, he asked his manager and coaches, "Where are our black players?" There was a long silence and one of the coaches finally said, "We don't have any." Busch said, "How can it be the great American game if blacks can't play?" The silence hung heavily over everyone. "Hell," he added, in words that clearly represented the end of an era, "we sell beer to everyone."