It says early 1900s, so no. It does largely refer to farming, but farming was insanely lucrative during that time. Look at the farms that have the houses of that era standing on them and you'll soon notice that they are all mansions.
Remember, subsistence farming first had to end before people could start working off the farm. Someone has to feed them too. For 50% of the workforce to be working a job off the farm, the other 50% being subsistence farmers would be impossible.