(CNN) -- A bipartisan group of lawmakers in Washington State voted Wednesday in favor of a bill that would legalize same-sex marriage, putting Washington on the path toward becoming the seventh state in the nation to legalize marriage for gay and lesbian couples.
"With today's vote, we tell the nation that Washington state will no longer deny our citizens the opportunity to marry the person they love," said Gov. Chris Gregoire, a Demorcrat who has vowed to sign it. "We tell every child of same-sex couples that their family is every bit as equal and important as all other families in our state. And we take a major step toward completing a long and important journey to end discrimination based on sexual orientation."
The law will go into effect in June, when the legislative session ends, unless opponents halt its implementation by putting it on the November 2012 ballot.
The 55-43 vote in the House included two Republicans in support of the bill. The Senate vote last week was 28-21 and included four Republicans.
"Like thousands of other same-sex couples, my partner Eric and I are very grateful for these protections that the law now provide," said state Rep. Jamie Pedersen, a Democrat, moments before the vote. "But domestic partnership is a pale and inadequate substitute for marriage."
State Rep. Jay Rodne, a Republican, disagreed. "Marriage is about life," he said. "It's about joining that man and that woman as husband and wife and mother and father, linking them with their natural-born children or adoptive parents and carrying forward our civilization."
The National Organization for Marriage, which opposes the law, has said it will seek to gather the 120,577 signatures needed to put the issue to voters as a referendum in November. The group did not immediately return a call.
Joseph Backholm, director of the Family Policy Institute of Washington, has said the issue should be put to a public vote. "If we as a state are going to take the position that mothers and fathers are interchangeable and replaceable, if we are going to send a message to fathers and potential fathers in this state that it isn't important to be in the lives of their children because dads specifically don't matter, that is something we should all do together," he said last month.
But Thalia Zepatos, director of public engagement for Freedom to Marry, questioned the fairness of a vote. "Is it appropriate for all the voters to vote on the rights of a small minority group of people?" she asked.
Advocates of same-sex marriage have followed several paths toward legality in Massachusetts, Vermont, New Hampshire, Connecticut, Iowa, New York and the District of Columbia. "In each state, the question of marriage has come up either through the courts, through the legislatures or directly at the ballot," Zepatos said. "I think this demonstrates the growing support nationally amongst Republicans, Democrats and Independents who see that allowing committed and loving, same-sex couples to get married does not take anything away from the marriages of their friends, neighbors and family members."
The benefits of same-sex marriage translate into benefits for the larger community, said Zepatos, citing one study that predicted $88 million in additional spending would occur in Washington once the practice becomes legal. "It's a real boost for small business in particular," she said.
In 2009, Maine state legislators passed a same-sex marriage bill that drew subsequent challenges by opponents who pushed for a referendum that ultimately overturned the law with 53% of the vote. Proponents are trying to get it back on the ballot this year. Gay rights advocates have already garnered thousands of signatures in an effort to force a second referendum in November.
In California, a 2008 public vote outlawed gay and lesbian couples' right to wed.
Two years later, a federal district court overturned the voter-approved measure known as Proposition 8, saying couples were unfairly denied their rights. A federal appeals court ruled Tuesday against California's ban, arguing that it unconstitutionally singles out gays and lesbians for discrimination.
The ban has remained in place during the appeals process and could soon get a ruling from the U.S. Supreme Court.
Similar battles have unfolded in Maryland, where same-sex marriage opponents have pressed for referendums to counter bills that appear to enjoy growing support in their state houses.
CNN's Tina Burnside contributed to this story