(CNN) -- Gov. Martin O'Malley will sign into law Thursday a bill legalizing same-sex marriage in Maryland, making it the seventh state to do so.
"All children deserve the opportunity to live in a loving, caring, committed, and stable home, protected equally under the law," O'Malley said in a statement after the vote.
The Maryland House of Delegates approved the measure less than two weeks after Washington legislators voted to legalize same-sex marriage. That measure will take effect in the summer if it survives a likely court challenge.
Six states and the District of Columbia already issue same-sex marriage licenses -- Connecticut, Iowa, Massachusetts, New Hampshire, New York and Vermont. Five states -- Delaware, Hawaii, Illinois, New Jersey and Rhode Island -- allow civil unions that provide rights similar to marriage.
New Jersey lawmakers approved same-sex marriage this month, but Gov. Chris Christie vetoed the legislation. He has said voters should decide the issue in a statewide referendum.
Voters in North Carolina and Minnesota, meanwhile, will consider proposals in May and November, respectively, to ban gay marriage in those states. New Hampshire lawmakers may also consider a repeal of its same-sex marriage law, according to the National Organization for Marriage, which opposes same-sex marriage. Lawsuits seeking to expand civil unions or turn back laws banning same-sex marriages are working through the courts in at least 12 states, including Hawaii, Minnesota and California, the organization said.
Same-sex marriage became a national issue in 1993, after the Hawaii Supreme Court ruled that a ban on same-sex marriages violated the state constitution.
Legislation was introduced recently to allow same-sex marriages in Illinois, and bills from 2011 remain technically active in Hawaii and Minnesota, said Jack Tweedie of the National Council of State Legislatures. It's unclear whether any will see significant action, he said.
An effort is also underway to put a proposal to legalize same-sex marriage on the November ballot in Maine, where voters previously overturned a 2009 state law authorizing same-sex marriage.
In California, meanwhile, a federal appeals court recently ruled against a voter-passed referendum that outlawed same-sex marriage. It said such a ban was unconstitutional and singled out gays and lesbians for discrimination. The case appears to be eventually headed to the U.S. Supreme Court.