The following characteristics are considered "Protected Classes" and persons cannot be discriminated against based on these characteristics:
Race - Federal: Civil Rights Act of 1964 and the Civil Rights Act of 1866
Color - Federal: Civil Rights Act of 1964
Religion - Federal: Civil Rights Act of 1964
National origin - Federal: Civil Rights Act of 1964
Age (40 and over) - Federal: Age Discrimination in Employment Act of 1967
Sex - Federal: Equal Pay Act of 1963 & Civil Rights Act of 1964
Familial status (Housing, cannot discriminate for having children, exception for senior housing)
Sexual orientation (in some jurisdictions and not in others)
Gender identity (in some jurisdictions and not in others)
Disability status - Federal: Vocational Rehabilitation and Other Rehabilitation Services of 1973 & Americans with Disabilities Act of 1990
Veteran status - Federal Vietnam Era Veterans Readjustment Assistance Act of 1974
Genetic information - Federal: Genetic Information Nondiscrimination Act