Here's how you know baseball is an old, old sport: the size, weight and design of the baseball, as regulated by the MLB, have been almost identical for almost 140 years. Since the late 1870s, the baseball has been "a sphere formed by yarn wound around a small core of cork, rubber or similar material, covered with two strips of white horsehide or cowhide, tightly stitched together. It shall weigh not less than five nor more than 5.25 ounces avoirdupois and measure not less than nine nor more than 9.25 inches in circumference." The late 1870s! And yet, for decades before then, baseballs varied dramatically in size, weight, and even material.
The balls were all handmade for decades, sometimes by pitchers themselves. It's hard to imagine how much unpredictability this added to the game, but Smithsonian Mag's piece on the history of the baseball does a good job of charting the early days of the ball, before it gained its famous red stitching. In some early balls, sturgeon eyes were used in place of melted rubber cores. The leather covering on some on early balls was nicknamed the "lemon peel" thanks to its four distinct lines of stitching.
The lemon peel balls, Smithsonian Mag writes, "were smaller –about six inches in circumference compared to today’s nine- and they were lighter (in weight), darker (in color) and softer (in softness) than those used today. And the game was a little different too. In the earliest games, runners could be thrown out by getting “soaked,” or hit directly with a ball by a fielder – a rule still occasionally practiced on playgrounds and sandlots. These light, compact balls with rubber (or fish-eye) cores were much “livelier” than today’s balls – that is to say, the could be hit further and bounce higher."
Some ball clubs elected to standardize the ball to between 8 and 11 inches in circumference and 5.5 to 6 ounces in weight, but that still left plenty of room for variation. The figure eight stitching design came into popularity in the 1860s, but the real standardization kicked in in the 1870s.
"The year 1876 welcomed the first game in the National League of Professional Baseball Clubs and a standardization of rules and regulations – including a standard ball," writes Smithsonian Mag. "That same year a Boston Red Sox pitcher by the name of A.G. Spalding retired after winning 241 of 301 games in just a four-year career. He pitched every game with balls he made himself. When he convinced the National League to adopt his ball as its standard, an empire was born. Spalding’s company would continue to produce the official baseball of the National League for 100 years."
For a few decades, this ball design led to low scoring games. The rubber in the ball would go dead and balls were played until they fell apart. But in 1910, baseball switched over to a cork center, which was more resilient, and hitters got crackin'. Check out the rest of the baseball's history to read up on its last big change to an even livelier cork-and-rubber interior. The ball still hasn't changed much in the past 90 years--each and every red stitch, for example, is still done by hand.