Anti-discrimination law
The Civil Rights Act of 1964 was the first major development in anti-discrimination law in the US, though prior civil rights legislation (such as the Civil Rights Act of 1957) addressed some forms of discrimination, the Civil Rights Act of 1964 was much broader, providing protections for race, color, religion, sex, or national origin in the areas of voting, education, employment, and public accommodations. This landmark legislation led the way for other federal legislation, which expanded upon the protected classes and forms of discrimination prohibited under federal legislation, such as the Fair Housing Act or the Americans with Disabilities Act. These protections have also been expanded through the courts interpretation of these pieces of legislation. For example, the 7th and 2nd circuit courts have both ruled that employment discrimination based on sexual orientation is a violation of Title VII of the Civil Rights Act. In addition to federal legislation, there are numerous state and local laws that address discrimination that is not covered by these laws.
United States labor law
Some state and federal laws presume workers who are not covered by a collective bargaining agreement or an individual employment agreement have "at-will employment". This is a policy that employees' may be dismissed without notice and for no stated reason. However state and federal laws prohibiting discrimination or protecting the right to organize or engage in whistleblowing activities modify that rule by providing that discharge or other forms of discrimination are illegal if undertaken on grounds specifically prohibited by law. An employment relationship could be terminated by either party at any time without a reason. Starting in 1941, a series of laws prohibited certain discriminatory firings. That is, in most states, absent an express contractual provision to the contrary, an employer can still fire an employee for no or any reason, as long as it is not a reason in violation of public policy.