across the country, as it re-elected Democratic President Barack Obama for four more years.
Obama came out in favor of gay marriage months before the election which pitted him against Republican rival Mitt Romney, who insists that marriage should be reserved for a relationship between a man and a woman.
During his first four-year term Obama had also fulfilled a pledge to repeal the controversial Don't Ask Don't Tell (DADT) law banning openly gay servicemen and women from serving in the US military.
Three states voted Tuesday to legalize same-sex marriage, including Maine -- which voted in a referendum against it in 2009, but reversed that decision with 54 percent in favor to 46 percent against.
Washington state and Maryland also appeared set to approve the move, which had already been passed by state lawmakers. Both states voted 52-48 percent in favor, according to CNN projections based on partial results.
Same-sex marriage is not federally recognized, but it was already legal in Connecticut, Iowa, Massachusetts, New Hampshire, New York, Vermont and the District of Columbia. It is constitutionally banned in 31 states.
Meanwhile three states -- Colorado, Washington and Oregon -- voted on proposals to legalize marijuana including for recreational use, going further than a number of states which already allow it for medicinal purposes.
Colorado backed the move by 54 percent in favor to 46 percent against, and Washington by 55 percent to 45 percent, according to CNN citing partial results. Oregon rejected it by 56 percent to 44 percent, it said.
Florida voters meanwhile rejected a proposal to ban the use of public funds for abortion or for insurance coverage for the service, according to partial results.
Fifty-five percent of voters rejected Florida's so-called Amendment 6, with 45 percent in favor, according to NBC and CNN.
Abortion has long been a hugely divisive issue in America, with many Republicans fiercely opposed. During the campaign two Republican politicians made controversial comments which fueled the debate.
In Missouri Republican candidate Todd Akin triggered a firestorm by suggesting that a women's body could shut down conception in cases of "legitimate rape."
Then more recently in a hotly contested Senate race in Indiana, Republican Richard Mourdock was criticized for suggesting that if a woman becomes pregnant from rape, it is "something that God intended to happen."
Both Akin and Mourdock were beaten in their respective poll races on Tuesday, according to US networks.
Other closely watched ballot races included two in California: one to force food companies to provide labels for genetically modified (GM) ingredients in their products, which appeared set for rejection.
A vote on banning the death penalty -- replacing it with life in prison without parole -- appeared set to be rejected with 56 percent against and 44 percent in favor, according to CNN with 25 percent of votes counted.