I spent Tuesday making my first visit to the National Baseball Hall of Fame and Museum in Cooperstown, New York. There is a large oil painting of Civil War general Abner Doubleday as you enter the waiting room for the introductory movie, and a brief discussion of the 1905 account by a local resident that first linked Doubleday to the origins of the game of baseball. During his lifetime, the general made no such claims, but the Cooperstown citizen sent a letter to the men studying the origins of baseball and purported that Doubleday had indeed written the first rules. Later, an old baseball was found in the letter writer’s attic in a trunk as his personal effects were being inspected. This seemed to give further credence to the story. The myth that Abner Doubleday invented baseball persists today, even in some Civil War and Gettysburg books.
Baseball was indeed played in the Civil War, and I have read a few accounts of ball games being played during rest breaks during the Gettysburg Campaign. It was more popular in the Northern army, but was not unknown to Southerners. There are a couple of good books on the subject that are worth reading for additional information.