Between July 2018—June 2019, 49 horses died at the Santa Anita race track in Southern California. The story of the dead horses spread— from the trade publications to The New York Times to Good Morning America until journalists, politicians, and DA investigators started to ask: should American horse racing still exist? From ESPN Investigates, Bloodlines examines horse racing’s current existential crisis. How did horse racing go from America’s most popular sport to a game driven by returns on investment? How have decades of breeding for races changed the horses themselves? And what might the dead horses at one track mean for the future of horse racing?