A significant shift in population from the Eastern and Midwestern United States to the West and South after World War II wreaked havoc with the established 16-team, two-league major league structure, opening up growing markets and triggering a two-decade-long series of franchise relocations beginning in . In , these were dramatized by the transfer of each of New York City's National League teams, the Dodgers and Giants, to California, abandoning their established fan bases. When New York attorney William Shea was unsuccessful in his attempts to attract Senior Circuit teams from smaller markets (including the Pirates) to New York, he announced plans for a third major league in professional baseball, the Continental League, on July 27, 1959. In addition to New York, the Continental would be represented by clubs in Denver, Houston, Minneapolis–Saint Paul and Toronto, plus three additional markets to round out an eight-team league. It was scheduled to begin play in April 1961.