Most cricketers have heard that baseball developed out of an early form of cricket (called "rounders"). But the full story is more complicated, and says a great deal about early cricket in America as well.
According to the United States Sporting Goods Manufacturers Association (US-SGMA), those English immigrants who had settled in New York spent their free time playing cricket in the 1700s.
Up the coast in Boston, cricket was also played by English immigrants, notably those who considered themselves as gentry.
But Boston had begun quite early on to acquire both a plebean and an Irish flavor. The game of rounders, an earlier form of cricket which seems to have been favored by the Irish, as well as by English children in the 16th century, became the game of choice among the youth.
The Boston cricketers of the time encouraged "Rounders" as a secondary diversion, and even allowed it to be played in their cricket fields by those who preferred an alternative to the more formal sport of cricket.

So "early baseball", i.e. " US Rounders", grew up in the USA under cricket's benign umbrella. It stayed that way for about the first hundred years of its existence.

In the 1750s, US Rounders involved only two bases, probably because cricket (of that time and later) used a two-base system as well.
The pitcher was known then as the 'feeder,' the batter was called the 'striker,' and the fielders were referred to as the 'scouts.'
Basically, the 'feeder' threw a slow, underhand pitch from one base to the 'striker' at the other, exactly where he was asked to deliver it. (If the 'feeder' failed to satisfy the 'striker's' requests, the 'striker' could demand that the 'feeder' be replaced!) The 'striker' would hit the ball as far as he could, and this would enable him to run back and forth between his original position and the other stake, each successful run scoring a point.
The scouts or the feeder would field the ball, and try to hit the striker with the ball before he could finish his run and grab the base he was running to (he would be "safe" as long as he was holding the post which served as a base).
In other words, the MAJOR differerence between early Rounders and Cricket in North America was that the bowler/pitcher had no role in getting the batter out...the batter could only be "run out" or "caught".

As more participants joined the game, they set out more stakes around which the 'striker' had to run before getting back 'home.'...giving the "scouts" more targets to throw at !
With the changes in rules, came a name change as well. Instead of "Rounders", the game now began to be called "Townball," i.e. an urban sport… unlike cricket, which was then a bucolic and leisure-class activity.
The stakes which functioned as bases in "Townball" were much closer to each other than the bases in a modern-day baseball diamond---20 yards, as opposed to today's 30 yards. Also, their disposition was "square", not diamond-like. The number of bases or stakes were usually four by the early 19th century, although earlier they had varied from two to five. And the pitcher/ feeder stood only 12 yards away from the batter/striker, whose position was between the First and Fourth stakes, about 10 yards away from each.

Look at the following diagram, comparing Boston's 1850s Townball "square" with the standard cricket pitch.

You can easily see, from the diagram, how a Townball "square" could develop from cricket net-practice sessions.
Just imagine a practice "pitch" on the side of a cricket field, and extend both popping creases 20 yards into the field. You will have a Townball "square"... and an excellent post-game cricket exercise in batting and fielding! And that was exactly how early baseball first developed, out of 19th-century US cricket...

Not to be outdone by Boston, the New Yorkers renamed their version of rounders 'The New York Game'. They fixed the number of stakes at four bases instead of two wickets.
A complete batting order where all persons had batted was termed a 'hand', exactly as in early cricket, but batting would rotate between the opposite sides on every 'out'. A complete trip around the bases was called an 'ace.' For the New York Game, the winner was the first team to score 21 aces, i.e. bring 21 runners "home".
As the New York Game became established, in 1845 a young surveyor by the name of Alexander Cartwright designed the first baseball diamond, departing from Boston's "Town Square" design. A year later in Hoboken, NJ, 'The New York Game' was played on a field using Cartwright's dimensions. The contest featured the New York Nine vs. the Knickerbocker Club.
Each club had nine players, apparently for no better reason than that New York insisted on that number....and in those days, what New York wanted, New York got.

The arrival of the Civil War helped spread the popularity of the ' New York Game.' Many soldiers from the Northeast were seen carrying their equipment while on duty. After the Civil War, the game became a popular activity, as every hamlet, village, town, and settlement formed a team.
A challenge match between teams from nearby communities was often the setting for a local holiday.
As interest in baseball rose, changes were made to ensure the game's continued popularity.
For instance, by the early 1800s a round bat was used instead of a flat cricket bat. Modern cricket bats are expensive and individualized to suit the tastes of different batters, while baseball bats can be used by just about anybody who wants to play. All players (including the catcher) started using padded mitts and protective gear when necessary.
More importantly, the rules were also changed to give back the 'feeder' or 'pitcher' more of a role in getting batters out.
First, they were allowed to pitch as they wished, not how the striker wanted him to (as in rounders). Then, the batter was restricted to three "strikes" (i.e. "misses") on accurate pitches, but earned a free base run after four inaccurately thrown pitches (the "four balls" rule)...meaning, a batter was on base for no more than 5 to 10 pitches every time he came in to bat.
Scoring hits were soon restricted to the spaces between the bases facing the batter. Another change: Previously, the batting side would change on every "out", but both sides would keep batting until 21 runners had been brought safely "home". Now, the team bringing more runners "home" for a given number of "outs" was allowed to claim victory.
Finally, allowing each inning to consist of three "outs" effectively replaced the old "hands" into three batting forays per side... and, by alternating these new "innings", each team got the chance to match or surpass the other's score throughout the course of the game. This increased the suspense of winning or losing, always an important factor in American sport.

There is a hidden irony in the way things happened, in both baseball and cricket.
Early baseball (i.e. US rounders) was supposed to give batters more opportunities than in cricket, by reducing the role of the pitcher/bowler to that of "feeder". Yet todays' baseball is a pitcher's game....while modern cricket is the sport that really gives batters the major role !
Baseball and cricket, then, came from very similar backgrounds.
They looked a lot like each other, in baseball's early days.
But, after 1850, the two games drifted apart... and each assumed its own character and identity.

Cricket became a longer and more leisurely game as batters (batsmen) began to dominate the sport, and wanted more time to display their individual skills.
Baseball, on the other hand, became shorter and more abbreviated....pitchers assumed an active rather than passive role, then came to dominate the sport; baseball batters were allowed fewer and fewer options, could spend less time at bat, and the rules were changed to favor shorter games.

By the 1900s, cricket and baseball were looking far more different from each other than in baseball's earlier years.

And by that time, it had become an issue of "cricket OR baseball" in the USA...and everyone knows what happened.