The first civil rights laws protected only race and color. As the principle of discrimination evolved over the years more laws were passed and more groups were added. Federal protected classes now include race, color, national origin, religion, sex (or gender), age (over 40), and disability. State law (HEPA) further protects ancestry, marital status, sexual orientation, as well as arrest and court record (in most cases).
Anti-discrimination laws only regard unequal or unfair treatment as unlawful discrimination when the victim is a member of a defined group known as a protected class.