I am not a lawyer, so take this with a big grain of salt. The Equal Pay Act (EPA) of 1963 says that it is unlawful in the United States to pay women less salary than men for work that is "substantially equal." The law specifies that men and women must be paid equally for similar work unless the salary difference is based on seniority, experience, or other legitimate factors. At the time of the EPA’s passage, women made 58 cents for every dollar brought home by their male counterparts. The EPA was established to level out this salary imbalance.