4BC News: Voters a continent apart have made history on two divisive social issues, with Maine and Maryland becoming the first states to approve same-sex marriage by popular vote, while Washington state and Colorado legalised recreational use of marijuana.

The outcome in Maine and Maryland on Tuesday broke a 32-state streak, dating back to 1998, in which gay marriage had been rebuffed by every state that voted on it. They will become the seventh and eighth states to allow same-sex couples to marry.

"For the first time, voters in Maine and Maryland voted to allow loving couples to make lifelong commitments through marriage - forever taking away the right-wing talking point that marriage equality couldn't win on the ballot," said Chad Griffin of the Human Rights Campaign, a national gay-rights group.

Washington state also was voting on measures to legalise same-sex marriage, while Minnesota voters were considering a conservative-backed amendment that would place a ban on same-sex marriage in the state constitution.

The marijuana measures in Colorado and Washington set up a showdown with the federal government, which outlaws the drug.

Colorado's Amendment 64 will allow adults over 21 to possess up to an ounce (28 grams) of marijuana, though using the drug publicly would still be banned. The amendment would also allow people to grow up to six marijuana plants in a private, secure area.

Washington's measure establishes a system of state-licensed marijuana growers, processors and retail stores, where adults can buy up to an ounce (28 grams). It also establishes a standard blood test limit for driving under the influence.

The Washington measure was notable for its sponsors and supporters, who ranged from public health experts and wealthy high-tech executives to two of the Justice Department's top former officials in Seattle, US Attorneys John McKay and Kate Pflaumer.

"Marijuana policy reform remains an issue where the people lead and the politicians follow," said Ethan Nadelmann of the Drug Policy Alliance, which opposes the co-called "war on drugs".

"But Washington state shows that many politicians are beginning to catch up."

Estimates show that pot taxes could bring in hundreds of millions of dollars a year, but the sales won't start until state officials make rules to govern the legal weed industry.

In Massachusetts, voters approved a measure to allow marijuana use for medical reasons, joining 17 other states. Arkansas voters were deciding on a similar measure that would make it the first Southern state in that group.

Maine's referendum on same-sex marriage marked the first time that gay-rights supporters put the issue to a popular vote. They collected enough signatures over the summer to schedule the vote, hoping to reverse the outcome of a 2009 referendum that quashed a gay-marriage law enacted by the state Legislature.

In both Maryland and Washington, gay-marriage laws were approved by legislators and signed by the governors earlier this year, but opponents gathered enough signatures to challenge the laws.

In Minnesota, the question was whether the state would join 30 others in placing a ban on gay marriage in its constitution. Even if the ban is defeated, same-sex marriage would remain illegal in Minnesota under statute.

Heading into the election, gay marriage was legal in six states and Washington DC - in each case the result of legislation or court orders, not by a vote of the people.

In California, voters were deciding whether to repeal the state's death penalty. If the measure prevailed, the more than 720 inmates on death row there would have their sentences converted to life in prison.

While 17 states have ended capital punishment, most did so through legislative action. Only in Oregon, in 1964, did voters choose to repeal the death penalty; they later reversed themselves to reinstate it.

In all, there were 176 measures on the ballots on Tuesday in 38 states, according to the Initiative and Referendum Institute at the University of Southern California.

Other notable ballot measures:

- Maryland voters approved a measure allowing illegal immigrants to pay lower in-state college tuition, provided they attended a state high school for three years and can show they filed state income tax returns during that time. About a dozen other states have similar laws, but Maryland's is the first to be approved by voters.

- In Oklahoma, voters approved a Republican-backed measure that wipes out all affirmative action programs in state government hiring, education and contracting practices. Similar steps have been taken previously in Arizona, California, Michigan, Nebraska and Washington.

SOME OF THE KEY MEASURES VOTED ON BY AMERICANS IN THE US CONGRESS ELECTION, NOVEMBER 6, 2012

SAME-SEX MARRIAGE

Maine and Maryland become the first states to approve same-sex marriage by popular vote

LEGALISING MARIJUANA

Washington state and Colorado legalise the recreational use of marijuana, setting up a showdown with the federal government, which outlaws the drug.

DEMS KEEP SENATE

Democrats won a narrow majority in the Senate, keeping the control they've held since 2007, by snatching Republican-held seats in Massachusetts and Indiana and turning back challenges in Virginia, Ohio and Connecticut.

Republicans were undone by stumbles in Missouri and Indiana, with candidates' clumsy statements about rape and abortion doing severe damage to their individual chances - and their party's hopes of taking over.

Heading into this election, with 33 seats up for grabs, Democrats held a 53-47 edge in the Senate, including the two independents who caucus with them. So Republicans needed a net gain of four seats to grab the majority. Shortly after 11pm, Democrats gained a lock on 50 seats, enough to keep control once Obama won re-election.

Senate Majority Leader Harry Reid spoke of conciliation.

"Now that the election is over, it's time to put politics aside and work together to find solutions," Reid said in a statement. "The strategy of obstruction, gridlock and delay was soundly rejected by the American people. Now they are looking to us for solutions."

MCCASKILL WINS AFTER AKIN RAPE COMMENT

Missouri Senator Claire McCaskill, a Democrat once thought to be one of the Senate's most vulnerable incumbents, held on to her seat in Tuesday's election as GOP challenger Todd Akin continued to face criticism for saying in August that women had ways of preventing pregnancies in the case of "legitimate rape". GOP leaders, including Republican nominee Mitt Romney, called on him to abandon the race. Akin stayed in and hoped support from evangelicals would lift his prospects.

DOWN FOR THE COUNT

Former World Wrestling Entertainment executive Linda McMahon - a Republican and wife of blustery and better-known Vince McMahon - lost her bid for a US Senate seat to Democrat Chris Murphy despite spending $US42 million ($A40.41 million) of her own wealth.

She also was beaten in 2010 while trying to get to the Senate.

Murphy now takes over the seat held by retiring independent Senator Joe Lieberman. Murphy, a three-term congressman, made an issue of the 64-year-old McMahon's wrestling roots, dismissing the enterprise as a vulgar and violent spectacle that belittled women.

In another Senate race with a link to the world of sports, the great-grandson of one of baseball's most august figures lost his Senate race in Florida. Connie Mack IV, a Republican, is a descendant of Hall of Fame manager Connie Mack. He was beaten by Democrat Bill Nelson, who won a third term.

Mack was not the only loser on the ballot with a strong baseball heritage. US congressman Ben Chandler of Kentucky, grandson of former baseball commissioner Happy Chandler, lost to Republican Andy Barr.

QUICK QUOTE: SPEAKER BOEHNER

"For two years, our House majority has been the primary line of defence for the American people against a government that spends too much, taxes too much and certainly borrows too much. ... We stand ready to work with any willing partner - Democrat, Republican or otherwise." - House Speaker John A. Boehner, an Ohio Republican.

WARREN OVER BROWN IN MA

Democrat Elizabeth Warren has defeated Republican Senator Scott Brown in Massachusetts. Brown came to the Senate in January 2010 after a surprise win in a special election to fill the seat of the late Democratic Senator Edward Kennedy. This year's senate campaign was one of the election season's most expensive, with the candidates spending $US68 million. Brown vowed to be an independent voice in the Senate but couldn't hold on in a presidential election year in the Democratic-leaning state.

MOURDOCK LOSES IN INDIANA

Republican Richard Mourdock - who slipped in the polls after saying during a debate that when a woman who is raped becomes pregnant, it's "something that God intended" - lost his US Senate race in Indiana to Democrat Joe Donnelly. Mourdock is a tea party-backed state treasurer who surprised the GOP when he beat six-term Senator Richard Lugar in the primary. His debate comment last month re-shaped the tight Indiana race for the Senate.