In the vast majority of states, parties of the same sex are legally forbidden to marry each other. Many states have a specific law or constitutional amendment proscribing such marriages. However, same-sex persons can marry in the states of Connecticut, Maine, Massachusetts, New Hampshire, Vermont, and Iowa. As of December 2009, the District of Columbia appeared close to allowing such marriages as well.

New York recognizes same-sex marriages from other states but does not allow them to be performed within its borders. Several other states—mainly in the northeastern region of the country—permit civil unions between persons of the same sex. In November 2008, Connecticut passed a law allowing civil unions between members of the same sex. In 2009, the Iowa Supreme Court legalized gay marriage. In April 2009, Vermont passed a law legalizing gay marriage. In May 2009, the Maine legislature passed a law allowing gay marriages. In June 2009, the New Hampshire legislature also passed a law allowing such marriages.

The California Supreme Court also legalized gay marriage in 2008, but then the state constitution was amended to prohibit such marriages.