The correct answer to this open question is the following.
The changes that led to the rise of the mass culture around 1900 were the following.
At that time, American people started to get access to education, something that previously had not been an option due to the fact that most of them had to work hard in the farm fields or in the industry to feed their families. As more people learned to read, new information made them be interested in different things and they were able to buy newspapers and some books that allowed them to be informed, which also allowed them to have a better understanding of politics and social conditions of the time.
