From the very beginning, the American Civil War has been closely tied to the origins of baseball. Abner Doubleday, the sport’s mythical inventor, was a Union general in the war who fought at the decisive Battle of Gettysburg in 1863, and throughout the war, soldiers on both sides played the game when not marching or in battle to pass the time. As Steve Light writes, “Baseball came of age during [the] American Civil War.”
The evolution of town ball into the game of baseball began in Northern cities during the antebellum period, most notably in New York and Massachusetts. Two variants of the sport spread from both these regions, known respectively as the New York game and the Massachusetts game. Having evolved from the Knickerbocker Rules, the New York game began to spread via the National Association of Base Ball Players, the first formal organization of baseball clubs; despite its national aspirations, prior to the Civil War it was primarily a New York entity — all its founding members, for example, came from the five boroughs. The Massachusetts game, meanwhile, spread throughout the New England states, although it would occasionally be played outside them.
Rooted in the Knickerbocker Rules, the New York game took major steps in baseball’s evolution toward the modern game. Unlike earlier variants, you could retire a runner by stepping on the bag with the ball only if it was a force out; previously, every baserunner could be put out as if it were a force play. Starting in 1857, the 21-run endpoint was eliminated, with games instead ending after nine innings. Called strikes were introduced — previously, strikes were only the result of missed swings — while cricket-style flat bats were banned. In 1860, it was decided that it would be a good idea to mark the boundary between fair and foul territory with a white line — previously, the umpire essentially had to guess — as the modern field slowly began to take shape.
The Civil War proved to be a turning point in the evolution of baseball. Prior to 1861, the sport had a following throughout the country to such a point that the above political cartoon about the presidential election of 1860 used its imagery to promote Abraham Lincoln’s candidacy. It was still, however, largely an urban phenomenon, and a Northeastern one at that.
Over the course of the war, though, soldiers from both sides began to play as a means to stay in shape and pass the time. The number of games would peak during February, March, and April, when the weather was good enough on the front to play (remember, almost all battles in the war took place in the South), but the melting snows from the winter and spring rains made it difficult for armies to operate. From May through October, the war was fought, and when winter came around again and the armies found their winter shelters, the number of games would make a resurgence while the weather was still good enough. Although the Massachusetts game continued to be played among New Englanders, it was the New York version that came to be widespread, with officers even procuring bats and balls for their men to be able to play.
On the home front in the North, the National Association of Base Ball Players continued to meet during this time, while games became public events for spectators looking for entertainment and distraction from wartime worries. During these years, further rule changes came into effect. As some of these rules came from the Massachusetts game — for example, 1863’s decision to make it so that balls had to be caught on the fly to register as an out — it is likely that some of these rules spread into the New York game from New England regiments. Others, however, appear to be totally new innovations, intended to address one issue or another that had popped up. Sure enough, in 1863, a pitcher’s box and batter’s box were specifically marked, and in 1864, it was explicitly stated that a runner must touch every base in order.
Following the Civil War, the National Association of Base Ball Players, its similarly named successor, the National Association of Professional Base Ball Players, and the new National League continued to refine the game. Some rule changes, such as 1867’s decision to let the batter request where in the strike zone the pitch would be and 1887’s “four strikes per out”, did not last, while others — for example, the decision to classify foul bunts and caught foul tips as strikes in 1893 and 1894 — have remained in effect to this day.
Still others were tweaked many times before they found their modern form. Originally, a ball was called after three “unhittable” pitches, which meant that, although a walk was technically only three balls, it required nine “unhittable” pitches. In 1879, they officially set the number of balls for a walk at nine, decreeing that every pitch was either a strike, a ball, or a foul; that number would be reduced to eight in 1880, to six in 1884, to five in 1887, and finally to four in 1889. The modern pitcher’s mound, however, originated with a pitcher’s box that was 12 feet-by-4 feet in 1863, altered to 6-feet square in 1867, and reduced to 4 feet-by-5-and-a-half in 1887 before finally being removed in favor of the slab that a pitcher was required to push off of in 1893.
By the time the American League established itself as a major league in 1901, the game of baseball had largely come into the form that it exists in today. Meanwhile the rulebook has continued to evolve over the years: spitballs and other means of doctoring the ball were banned in 1920, the pitcher’s mound was reduced and the strike zone shrunk in 1969, the designated hitter was implemented in 1973, and the three-batter-minimum added in 2020. Compared to the changes that happened throughout the 19th century, none of these fundamentally changed the game, even if they altered how players and coaches approached it.