The correct answer is "they were paid far less than male workers doing the same job".
During the Industrial Revolution of the 19th century, factory owners saw women and children as an alternative cheap option in regards to labor. Women were able to perform tasks that did not require the level of expertise that would previously be required prior to the introduction of machines.
However, this would lead to women to fight for equality in regards to salary, as the gap between the income of men and women was important. Even nowadays for an important number of positions throughout organizations.