The sport of baseball has used statistics to enhance understanding for fans for over a century, yet there is limited data on player careers. This study fills that void by examining the careers of baseball players over the last century. Between 1902 and 1993, 5,989 position players started their careers and played 33,272 person years of major league baseball. A rookie position player can expect to play 5.6 years; one in five position players will have only a single-year career, and at every point of a player’s career, the chance of exiting is at least 11%. Position players who start younger and begin their careers in more recent decades all have longer and more stable careers; nevertheless, baseball careers are not compressed versions of normal careers, but are substantially skewed toward early exit.