Although in the United States, the majority age is 18 for nearly all the states, there are many ways that this age can be lowered.
Marriage: Most states will grant you at least freedom of control from parents and right to a residence if you get married, regardless of age. Some states will even grant right to enter in contracts. Most states allow you to marry at 16 without parental consent if it can be proven that the female is pregnant or has given birth.
Joining the active armed forces: At age 17, you are eligible to join the active armed forces. If you do so, all states will grant you at least some adult privileges. However, parental consent is required. Also, you need a high school diploma or GED certificate.
Applying for emancipation: Some states will allow children who are at least 16 years old to apply for emancipation if it can be proven that the child has a sufficiently paying job and is able to get a residence. Emancipation grants a child full adult status (except for voting, smoking,drinking, owning guns, etc.) However, most states that allow emancipation require parental consent.
If you are under 16, some states allow marriage (and partial adult status) with parental consent and proof of impregnation. Good luck!