The beginning of April means one thing for American sports fans: baseball is back. This year's first game will be held on Sunday, when the Pittsburgh Pirates host the St. Louis Cardinals.

According to legend , the game of baseball was born in 1835 in Cooperstown, N.Y.; the MLB was founded about sixty years later. And, though lots has changed between now and then, a game of late-19th-century baseball would still be recognizable to today's fans—including, as these photos show, the socks. And, though the modern baseball card is attributed to Sy Berger , who introduced Topps cards in 1951, its precursors were already around at that time, often in the form of studio portraits of players demonstrating the athletic poses that would have been seen on the field. (It was around that time, as The Atlantic has explained , that players' images also began to show up in cigarette packs as a "marketing gimmick.")

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These photos—some of which are undated but which appear to all come from the 1870s and '80s—are part of the A.G. Spalding baseball collection of the New York Public Library. Spalding, who will probably be most familiar today for the sports equipment that still bears his name, was a star in the early days of professional baseball, as a pitcher for the Chicago team that would eventually become the Cubs. He was also an aficionado of the game, publishing an annual guide for fans and gathering a large personal collection of baseball memorabilia, which his widow gave to the Library after his 1915 death.