The term "wrongful termination" is ambiguous because in the majority of states, employment is viewed as "at will". This means the law allows your employer to fire or terminate you for any reason or for no reason at all, except:
(1) Discrimination: Your rights are protected under employment discrimination laws. For example, employers cannot discriminate against you on the basis of age, sex, or gender, race, national origin, disability or perceived disability, pregnancy status, marital status, or sexual orientation.
(2) Retaliation: It is illegal for employers to fire employees for asserting their rights under the state and federal laws or complaining that work conditions don't meet state or federal rule.
(3) Contract: You have an employment contract with the employer. The contract states that you cannot be fired without just cause for a specific period of time. In other words, the reasons for which you can or cannot be fired will usually be pre-determined and stated within the contract.
It is best to consult an attorney to advise you whether you fit the conditions above because if you don't fit any of the conditions above, then generally it is not illegal for employers to terminate your employment.