Anti-discrimination legislation tends to become more inclusive over time, in two ways:
- more groups enjoy protection against discrimination (the disabled, transsexuals, older people, short people etc.) and
- discrimination becomes illegal in more social settings (employment, trade etc.).
I’ll focus here on employment discrimination, and more specifically discrimination on the basis of sexual orientation and gender identity.
Employment Discrimination laws seek to prevent discrimination based on race, sex, religion, national origin, physical disability, and age by employers. A growing body of law also seeks to prevent employment discrimination based on sexual orientation. Discriminatory practices include bias in hiring, promotion, job assignment, termination, compensation, retaliation, and various types of harassment. (source)
In the U.S., many states have laws that protect all public employees against employment discrimination, including discrimination of people based on their sexual orientation or gender identity. Many large cities and other localities have similar rules. A minority of states ban this type of discrimination in private employment: 21 states plus DC have laws banning discrimination in private employment that also cover sexual orientation, and 15 plus DC have laws that also cover gender identity.
Here’s a map showing those 21 and 15 states:

Legislation prohibiting employment discrimination on the basis of sexual orientation and Gender Identity in private employment
(source)
And here’s a map showing legislation covering both private and public employment:

Legislation Prohibiting Employment Discrimination on the Basis of Sexual Orientation and Gender Identity
(source)
An interesting new development: employers seem to be discriminating against the unemployed. When evaluating candidates for positions, employers prefer to hire someone who already has a job elsewhere. They often even announce in their job postings that they don’t hire applicants who aren’t currently working. Unemployed candidates, even if they have the same qualifications, are refused because their current lack of a job is supposed to signal laziness or other disqualifying characteristics. Some therefore propose to include also discrimination of the unemployed in legislation prohibiting employment discrimination. Others think that would be a bad idea subjecting businesses to frivolous lawsuits every time an unemployed person fails to get a job.