The Equal Pay Act of 1963 says that businesses cannot discriminate in providing wages to people who are performing equal work based on gender. That means that individuals who are handling the same responsibilities at the same quality level for the same period of time cannot make different wages solely because one is a women and one is a man. The act would likely also come into play in situations involving transgendered individuals.
The Civil Rights Act of 1964 goes even further. It protects people from discrimination in hiring or promotions based on gender as well as religion, race, national origin or color. This means that employers cannot base a decision between equally qualified candidates based solely on one of these factors. Businesses also cannot promote or choose not to promote a person based on these factors.