Is Man o' War, the legendary champion who revitalized American Thoroughbred racing, truly the greatest racehorse in history, or has time produced an even more extraordinary champion? Through meticulous research and compelling analysis, award-winning writer Mark Shrager presents the first comprehensive head-to-head comparison between the legendary "Big Red" and fifteen of history's most extraordinary Thoroughbreds. Moving beyond traditional metrics of wins and speed records, The Greatest Racehorse? examines Man o' War's legacy through dual lenses: his racing excellence against immortals like Secretariat and Citation and his transcendent cultural impact that helped save the sport itself. Set against the turbulent backdrop of World War I, Prohibition, and baseball's Black Sox scandal, this groundbreaking work reveals how Man o' War became more than just a champion--he was racing's savior when the sport faced potential collapse. Using rare historical records, statistical analysis, and insights from a forty-year career covering Thoroughbred racing, Shrager puts Man o' War's legendary status to the ultimate test. From dominating victories and record-setting performances to his enduring influence on breeding and American sports culture, The Greatest Racehorse? finally answers whether Man o' War's supreme reign can withstand the test of time and the challenges of racing's modern titans.