The Big List
Since you mention it, I have some issues with that entry.
(1) It strains to find an element of truth in the Abner Doubleday story. Abner Graves vaguely remembered an incident from his childhood, when as a young boy he was taught baseball by an older boy. Many decades later he was primed by the Mills Commission to interpret this recollection as being baseball’s origin. The Mills Commission was formed specifically to investigate the game’s origin. It’s primary research technique was to solicit reminiscences of old-timers, thereby implying that it believed the game to have been invented within living memory. Hence Graves being primed to remember the incident as an origin story. He was also primed to identify the older boy as Abner Doubleday, the Civil War general, by the mere fact of Doubleday’s fame. That it turns out that the local Cooperstown boy was the other Abner Doubleday doesn’t matter here, as it is entirely likely that Graves didn’t know this. So Abner Doubleday, the Civil War general, shared a name with a guy who was recalled (though with no good reason to believe the recollection) as having played baseball. To characterize this as an element of truth is a stretch.
(2) Alexander Cartwright, unlike Doubleday, actually did play baseball. There is not a scrap of contemporary or near-contemporary evidence that he had anything to do with the rules. He was a member of the Knickerbocker Club from 1845 to 1849, when he headed west as part of the California gold rush. There is no reliable (i.e. not forged) evidence of any involvement with baseball after he left New York. The one notable story about him and baseball is recorded in an 1866 book by Charles Peverelly. The book includes a fairly lengthy narrative history of the Knickerbocker Club. No original members were still active--the oldest active member had joined in 1850--but it is reasonable to understand Peverelly to be recording oral tradition within the club. The account has a group of men playing baseball informally since 1842. Cartwright is credited with having suggested they organize as a club. They formed a committee to recruit members. This is often played nowadays as Cartwright single-handedly creating the club through Herculean effort in the face of massive indifference. There is nothing in Peverelly to suggest this. The idea seems rather to have been taken up pretty enthusiastically. The key with respect to the rules is that they formed a committee to draft the rules. It comprised William Wheaton and William Tucker. There is some weak evidence for Duncan Curry, the first President of the club, as an ex officio member of the rules committee. Cartwright has no connection to it, and was not an officer in the club’s first year.
The various exaggerated claims about Cartwright’s involvement all came about in the early 20th century. William Rankin, a New York sportswriter, had a garbled recollection of an interview he had in 1877 with Duncan Curry. We know it is garbled because Rankin had published earlier versions. But during the Mills Commission he reacted strongly against the Doubleday story, adapted his memory of the 1877 interview to fit his needs, and presented his improved and implausibly detailed version with expressions of great confidence. People bought it. Then a few years later Cartwright’s grandson Bruce Cartwright got in the game, promoting his grandfather’s claim (which Alexander had never made), up to and including forging additions to Alexander’s wagon train diary.
So Cartwright, unlike Doubleday, did play a role in baseball history, but not the role he is typically assigned. How big a role depends on whether or not you can convince yourself that the idea of forming a baseball was a radical idea that only a genius could come up with. To convince yourself of this you have to be willing to overlook the presence of earlier baseball clubs, including in New York City. I know people who are up to the task of convincing themselves, but I am not made of stern enough stuff to manage it myself. (In the unlikely event that anyone is interested in the gory details, I published an article on the subject a couple of years ago in Baseball Research Journal.)
(3) Rounders. This is the best of the three. I would quibble about characterizing it as a “distant cousin” of baseball. In their pre-modern forms, baseball and rounders were one and the same game, or more accurately, family of closely related games. There were regional variations, but there are always regional variations. That is the nature of pre-modern games. There were regional variations in how baseball was played in different parts of America. Eventually both were standardized independently of one another, so different forms were codified. Baseball subsequently underwent rapid evolution through the second half of the 19th century, making the games more different from one another than they had been at the start of the process. Then in the 20th century baseball influenced rounders, so the games grew somewhat closer together. I would go with “siblings” rather than “distant cousins,” but as I say, this is a quibble.