 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.