In the early 20th century, progressive reforms were in their infancy, and had not yet made a huge difference in the daily lives of most American workers. Most Americans eked out a living on farms and in factories doing the hardest manual labor for the lowest pay.
Immigrants were the largest expendable supply of workers and generally lived in the poorer neighborhoods, in ramshackle apartment buildings. It was common that the entire family had jobs in order to make ends meet in the big cities.
The haves, on the other end of the spectrum, were obscenely wealthy. Mansions in fancy, well-protected neighborhoods were the norm and, like today, the rich lived a life mostly self-segregated from the rest of America. Politicians were often in the pocket of the wealthy (again, much like today) and so government policy continued to favor their wealth.
The key differences today are that there is a large middle class, and more or less permanent labor reforms such as the minimum wage, the 40 hour work week, weekends off, health care and retirement plans are all in place now, though a bit under siege. The disparity between rich and poor is still vast, and in fact, still growing, but there are fewer poor people by percentage than there was in the first two decades of the 1900s.