I just wanted to know what year did bathroom fans begin being put in houses. The house I grew up in was built in the 20's and didn't have a fan. There was a window.
I don't know when it became a requirement but building codes came into effect in 1955. If they were installed then it was by choice since no rule existed before then, that I know of. If an old code book can be found particular to you area, then it could be determined. But back in the day, the code was different area by area. Not greatly but small differences here and there, and still is, through local addendums. These addendums change the appropriate code to fit the local areas better, in some cases.
What I do know is that when the code did require fans in bathrooms, there was an exception if there was a window in the bathroom that opened, then it was not needed.
Oh, you definitely want a bathroom fan even if you have a window. There are two reasons you want to ventilate a bathroom, one is humidity from the shower. The "open window" method is not reliable for removing humidity, and that gets you mold. As for the other reason, half the time air blows in through the window, pushing bathroom air into the rest of the house - the opposite of what you want!