April 15, 1947, marked the most important opening day in baseball history. When Jackie Robinson stepped onto the diamond that afternoon at Ebbets Field, he became the first black man to break into major-league baseball in the 20th century. World War II had just ended; democracy had triumphed. Now Americans were beginning to press for justice on the home front— and Robinson had a chance to lead the way. But his biggest concern was his temper, and playing well, despite race-baiting by segregationists. Author Jonathan Eig, in addition to publishing three nonfiction books, writes a monthly sports column for Chicago magazine.