The heroine of Dreiser's novel grew up on a farm, like so many Americans of the times. At one time over ninety percent of Americans were subsistence farmers. It was common for country people to give the family children nicknames like Sister Carrie or Brother Bob. This was partly because subsistence farmers often had such large families. Theodore Dreiser himself came from a family with ten children. Families tended to be big because it was easy to grow a little more food or add another cow, and the children would wear hand-me-down clothes. Married people tended to know nothing about birth control and many probably believed it was sinful anyway.
The name Sister Carrie characterizes Caroline as a simple country girl. A secondary reason for the title was that Dreiser actually was writing about two of his own sisters who went to the big city and became prostitutes. And finally there is a suggestion that we should be tolerant of other people's misbehavior because, as the New Testament tells us, we are all brothers and sisters.
Dreiser was an extremely intelligent and perceptive as well as a compassionate man. He was writing about an important new social phenomenon in turn-of-the-century America. Farm girls like Carrie were leaving their homes in large numbers and moving to the big cities where there were new opportunities for women to earn money. Most of them took jobs in factories, as Carrie does at first. Some became office workers. (When Carrie is applying for jobs one of the interviewers asks her, "Are you a typewriter?" That was what typists were called in the early days.) She happens to be exceptionally good-looking, smart, enterprising, and ambitious; so it is probably inevitable that she does not remain confined to the drudgery of factory work for long. One of themes of the novel that shocked people when it was published is the suggestion that it is better for a single woman to be "kept" in comfort by a man than to exist as a low-paid factory slave doing what was called "piece work," i.e., getting paid for each separate item produced rather than on a per-hour basis. The lives of female factory workers are covered at greater length in Dreiser's masterpiece, An American Tragedy, arguably the best novel ever written by an American.