BOSTON (AP) — In the decade since the highest court in Massachusetts issued its landmark ruling legalizing same-sex marriage, 14 other states and the District of Columbia have legalized it, with Illinois poised to become the 16th in a few days.

Such gains were considered almost impossible before Massachusetts opened the door on Nov. 18, 2003, with a Supreme Judicial Court ruling that declared a ban on gay marriages unconstitutional. Opponents made doomsday predictions about how gay marriage would damage traditional marriage and lead to problems with children raised in same-sex households.

But as the years have passed, public opinion has shifted. Supporters have won in the courts, in state legislatures and on state ballots amid intense lobbying, activism and advertising campaigns filled with gay couples' personal stories.

"With more same-sex marriages, you saw more people changing their minds," said Mary Bonauto, civil rights project director at Boston-based Gay & Lesbian Advocates & Defenders and the lead attorney on the lawsuit that resulted in the gay marriage ruling in Massachusetts.

"Seeing gay people with their extended families, seeing the commitment, that's what has turned this around."

Opponents have shifted tactics as more and more states have legalized gay marriage. Initially, opposition focused on the predicted erosion of traditional marriage, but in recent years have pushed concerns about school curriculums and religious objections.

In New Mexico, the state Supreme Court ruled in August that an Albuquerque business owned by gay marriage opponents violated a state anti-discrimination law when it refused to photograph a same-sex couple's commitment ceremony. A law firm representing the business has asked the U.S. Supreme Court to hear its appeal.

Opponents say they plan to do a better job of telling similar stories of people who believe their religious freedoms have been infringed upon by the legalization of same-sex marriage.

"I think we still have to do litigation, we still have to do legislation, but we also have to do education as well," said Mathew Staver, founder and chairman of the Christian legal group Liberty Counsel.

Since same-sex marriages began in Massachusetts in 2004, approximately 100,000 gay couples have gotten married across the U.S., said Lee Badgett, a professor of economics at the University of Massachusetts-Amherst. At least 16,000 of the marriages have taken place in Massachusetts.

Evan Wolfson, founder and president of Freedom to Marry, said 38 percent of Americans will live in states where same-sex marriage is legal once Illinois's governor signs the bill on Wednesday. The group has a goal of bringing that up to more than 50 percent by the end of 2016.

"What we have to do — like other civil rights movements and social justice causes — is win a critical mass of states and a critical mass of public support, which together creates the climate for the Supreme Court to bring the country to national resolution," Wolfson said.

Wolfson said Oregon is expected to be a key battleground in 2014 as supporters hope to repeal a constitutional ban on gay marriage passed in 2004 during a rush of similar amendments in other states after the Massachusetts' ruling.

But Staver said he believes the momentum of the gay marriage movement will slow.

"Same-sex marriage represents a classic conflict with religious freedom," he said. "I think there will come a tipping point where the pendulum will swing the other way as people begin to see the impact of same-sex marriage."

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  • New York

    New York lawmakers <a href="http://www.huffingtonpost.com/2011/07/24/new-york-gay-marriage_n_907901.html" target="_blank">legalized same-sex marriage on July 24, 2011</a>, making it the largest state at the time to pass such legislation.

  • Maryland

    Voters in Maryland <a href="http://www.huffingtonpost.com/2012/11/07/gay-marriage-victory_n_2085900.html" target="_blank">approved marriage equality in the November 2012 election</a>. Initially, the gay marriage bill was signed into law by Gov. Martin O'Malley (D) on March 1, 2012, but opponents gathered enough signatures to force the issue back onto the ballot. With the passing of marriage equality, same-sex marriage <a href="http://www.huffingtonpost.com/2012/12/31/maryland-gay-marriage_n_2389044.html" target="_blank">ceremonies began on Jan. 1, 2013</a>.

  • Connecticut

    Connecticut's Supreme Court <a href="http://www.huffingtonpost.com/2008/10/10/connecticut-gay-marriage_n_133605.html" target="_blank">ruled that same-sex couples had the right to marry on Nov. 12, 2008</a>, making it the third state in the nation to do achieve marriage equality.

  • Iowa

    Iowa's Supreme Court <a href="http://www.huffingtonpost.com/2009/04/03/iowa-gay-marriage-ban-rul_n_182782.html" target="_blank">ruled the state's gay marriage ban unconstitutional</a> on April 3, 2009.

  • Maine

    Maine <a href="http://www.huffingtonpost.com/2012/11/07/gay-marriage-victory_n_2085900.html" target="_blank">made history in the November 2012 election</a> when it became the first state to pass marriage equality on the ballot. Human Rights Campaign President Chad Griffin said, "Voters in Maine came to the common-sense conclusion that all people deserve the ability to make loving, lifelong commitments through marriage." Just three years ago, a popular vote overturned legislation that would have legalized same-sex marriage in the state.

  • Massachusetts

    Massachusetts became the first state in the nation to <a href="http://www.history.com/this-day-in-history/first-legal-same-sex-marriage-performed-in-massachusetts" target="_blank"> legalize same-sex marriage on May 17, 2004</a>. The state's Supreme Court initially found the ban on gay marriage unconstitutional on Nov. 18, 2003.

  • New Hampshire

    Same-sex couples were able to <a href="http://www.cbsnews.com/2100-201_162-6042937.html" target="_blank">begin seeking marriage licenses</a> on Jan. 1, 2010.

  • Vermont

    Vermont, which invented civil unions, became <a href="http://www.huffingtonpost.com/2009/04/07/vermont-legalizes-gay-mar_n_184034.html" target="_blank">the first state to legalize gay marriage through a legislature's vote</a> -- overriding the governor's veto. Same-sex couples were able to begin marrying on Sept, 1, 2009.

  • Washington D.C.

    Gay couples were able to <a href="http://www.huffingtonpost.com/2009/12/01/gay-marriage-dc-council-p_n_375435.html" target="_blank">begin marrying in the nation's capital</a> on March 9, 2010.

  • California

    The state initially began conducting gay marriages on June 16, 2008. On November 5, 2008, however, California <a href="http://www.huffingtonpost.com/2013/06/26/proposition-8-timeline_n_3503512.html" target="_blank">voters passed Proposition 8</a>, which amended the state's constitution to declare marriage as only between a man and a woman. On June 26, 2013, by a 5-4 vote, <a href="http://www.huffingtonpost.com/2013/06/26/hollingsworth-v-perry-ruling_n_3438269.html" target="_blank">the Supreme Court justices held in Hollingsworth v. Perry</a> that the traditional marriage activists who put Proposition 8 on California ballots in 2008 did not have the constitutional authority, or standing, to defend the law in federal courts after the state refused to appeal its loss at trial, opening the door for marriages to resume in the state.

  • Washington

    On February 13, 2012, Gov. Christine Gregoire (D) <a href="http://www.huffingtonpost.com/2012/02/13/washington-gay-marriage-signed-chris-gregoire_n_1273887.html" target="_blank">signed a law allowing same-sex marriage ceremonies</a> to begin on June 7, 2012. The process was delayed by gay marriage opponents who gathered enough signatures to put the issue up to a state vote in November 2012. <a href="http://www.huffingtonpost.com/2012/12/09/washington-gay-marriage-law_n_2266574.html" target="_blank">Gay marriage passed on November 7, 2012.</a> The official determination for Washington did not come until one day after the election because of the state's mail-in voting system.

  • Rhode Island

    Gay marriage came to Rhode Island when Governor Lincoln Chafee <a href="http://www.huffingtonpost.com/2013/08/01/gay-marriage-minnesota-rhode-island_n_3686034.html" target="_blank">signed the marriage equality bill</a> into law on May 2, 2013.

  • Delaware

    Delaware obtained gay marriage when <a href="http://www.huffingtonpost.com/2013/05/07/delaware-gay-marriage-law-_n_3232771.html" target="_blank">Governor Jack Markell signed the marriage equality bill it into law</a> on May 7, 2013.

  • Minnesota

    Minnesota same-sex couples achieved marriage equality when Gov. Mark Dayton signed the legislation into law <a href="http://www.huffingtonpost.com/2013/05/14/minnesota-gay-marriage-legal-_n_3275484.html" target="_blank">on May 14, 2013</a>.

  • New Jersey

    Newark Mayor Cory Booker <a href="http://www.huffingtonpost.com/2013/10/20/cory-booker-same-sex-marriage_n_4134116.html?&ir=Gay%20Voices&utm_hp_ref=gay-voices" target="_blank">began marrying same-sex couples</a> at City Hall at 12:01 a.m. on Oct. 21, 2013.

  • Hawaii

    Hawaii Gov. Neil Abercrombie signed same-sex marriage into law on Nov. 13, 2013, making it the 15th state to pass such legislation.

  • Illinois

    Illinois became the 16th state to legalize gay marriage, with the House <a href="http://www.huffingtonpost.com/2013/11/05/illinois-gay-marriage_n_4220793.html" target="_blank">having passed the bill on Nov. 5</a>. and Gov. Pat Quinn signing the legislation on Nov. 20.

  • New Mexico

    On Dec. 19, the New Mexico Supreme Court <a href="http://www.huffingtonpost.com/2013/12/19/new-mexico-gay-marriage_n_4474507.html?ir=Gay%20Voices" target="_blank">unanimously ruled</a> that same-sex marriage rights are protected under the Constitution.