United States: Usually 18 years of age. Most states, however, allow marriage at a younger age with parental and/or judicial consent. Some states allow marriage at a still younger age if the female is pregnant.
Source: http://en.wikipedia.org/wiki/Marriageabl...

Emancipation in the United States of America

In the United States, a person is a minor (and therefore under the control of their parent(s)/guardian(s)) until they attain the Age of Majority (18 years). However, in special circumstances, a minor can be freed from control by their guardian, before turning 18. In most states, the three circumstances in which a minor becomes emancipated are: (1) enlisting in the military [requires parent/guardian consent], (2) marrying [requires parent/guardian consent], (3) obtaining a court order from judge [does not require parent/guardian consent].

Once a minor is emancipated, he/she is nearly equal to an adult, legally speaking. They are completely free from any control by their parent(s) or guardian(s).

Exact rights and responsibilities of emancipated minors vary by state. In most cases, an emancipated minor has the exact same rights and responsibilities as an adult, excluding the rights to purchase tobacco, pornography, lottery tickets, and firearms. Some (but not necessarily all) right of emancipated minors: emancipated minors can enter into contracts by themselves, sue and be sued in their own name, vote, obtain a drivers' license, seek medical care and consent to medical procedures, seek education or drop out of school, and hold a bank account. In most states, an emancipated minor will be tried as an adult if he/she is charged with a crime.

The exact laws and protocols for obtaining emancipation vary by state. In most states, the minor must file a petition with the family court in his/her jurisdiction, formally requesting emancipation and citing reasons why it is in his/her best interest to be emancipated. He/she must prove that he/she can support himself/herself financially. Many states require that the minor have been living separate from his/her parent(s)/guardian(s) for a period of time; however, that requires the consent of the parent(s)/guardian(s) in order to not classify simply as "running away".

Until an emancipation, or other legal mechanism, is granted by a court, a minor is still subject to the rules of their parent(s)/guardian(s).

Emancipations are rarely granted, because of the narrowness of the definition of "best interest". On one end of the spectrum are minors who have been victims of abuse; in most cases, the state's department of child services is notified and the child is placed in foster care. On the other end of the spectrum are minors who are seeking emancipation for superficial reasons, such as not being pleased with their parent's/guardian's rules. In those cases, the emancipation will most likely be denied.

In some states, free legal aid is available to minors seeking emancipation, through children's law centers. This can be very useful, in terms of creating a convincing emancipation petition.
Source: http://en.wikipedia.org/wiki/Emancipated...