Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. William Alexander O'Hara was a Major League Baseball outfielder. He started his professional baseball career in 1902 and played for the Baltimore Orioles from 1905 to 1908. He then played in the National League for the New York Giants and St. Louis Cardinals before finishing his career with the Toronto Maple Leafs. Major League Baseball (MLB) is the highest level of professional baseball in the United States and Canada, consisting of teams that play in the National League and the American League. The two leagues merged in 2000 into a single MLB organization led by the Commissioner of Baseball after 100 years as separate legal entities.