Book excerpt: Between 1915 and 1930, nine towns in the Blue Ridge Mountains of Pennsylvania, Maryland, and West Virginia hosted teams in one of the most successful Class D minor leagues in professional baseball. The Blue Ridge League launched the careers of legendary Hall of Famers Lefty Grove and Hack Wilson and served as a training ground or final stop for over 100 major-league players. This feisty league challenged laws prohibiting Sabbath baseball games (resulting in mass arrests of players and management), pioneered night baseball, served as a laboratory for the establishment of baseball's farm system, and helped develop a postseason five-state championship series.