Same-sex marriage has been legally recognized in Maryland since January 1, 2013. In 2012, the state's Democratic representatives, led by Governor Martin O'Malley, began a campaign for its legalization. After much debate, a law permitting same-sex marriage was passed by the General Assembly (Maryland's bicameral legislature, composed of the Senate and House of Delegates) in February 2012 and signed on March 1, 2012. The law took effect on January 1, 2013 after 52.4% of voters approved a statewide referendum held on November 6, 2012. The vote was hailed as a watershed moment by gay rights activists and marked the first time marriage rights in the United States have been extended to same-sex couples by popular vote.
Upon the rise of the same-sex marriage movement in the early 1970s, Maryland established the first law in the United States that expressly defined marriage to be a union between a man and a woman. Attempts to both ban and legalize same-sex marriage in the 1990s and 2000s failed to gain enough support from central committees of the state legislature. Roman Catholic authorities throughout the state were adamantly opposed to the legalization of same-sex marriage, saying it deeply conflicted with the best interests of society and would threaten religious liberty. The debates produced disputes between individuals who had been traditionally aligned on causes and prompted sharp criticism from African-American religious leaders who said same-sex marriage would "disrupt the fabric of the culture."