When Americans go to the polls on Tuesday, they will not just be choosing a president and members of Congress - there are 174 extra questions on the ballot in 38 states. And some go to the very heart of key issues in American society.

1. Marijuana

Three states - Oregon, Washington and Colorado - are voting on whether to legalise the sale and recreational use of marijuana.

Seventeen states, plus the District of Columbia, currently allow the sale and use of marijuana, but only for medicinal use.

It's not just about the president Also up for grabs on 6 November: 33 seats in the Senate

seats in the Senate 435 to the House of Representatives

to the House of Representatives 11 governors

governors 174 state-wide ballot measures Some Senate races to watch

The plans would see marijuana regulated in a similar way to cigarettes and alcohol, and would allow it to be sold to anyone 21 or over.

Proponents say it would generate millions of dollars in revenue for the state government, and free up courts and prisons for more serious offenders.

Opponents say it is a dangerous drug and that any state that passes the law - and polls suggest Washington and Colorado might - would then be on a collision course with federal government. Marijuana remains illegal under federal law, and federal law trumps state law.

Lawyers say it is hard to predict if federal government would step in. "We really don't know how it would play out," says Jennie Drage Bowser, an expert on ballot measures with the National Conference of State Legislatures.

2. Gay marriage

Voters in Maine, Maryland, Minnesota and Washington will vote in some form on gay marriage on election day.

In Maine, it is the first time that US voters are being asked if they want to legalise the unions (most ballots have been to ban them), and surveys suggest a majority are in favour.

Marylanders are voting on whether to uphold or reject a recent state law allowing same-sex marriage.

Thirty-one states across the US have passed constitutional amendments banning same-sex marriage in recent years, and nine have made it legal.

A Pew study in July suggests that, nationwide, more Americans now support gay marriage than oppose it, and that views have shifted significantly in favour in the past 10 years.

3. GM foods

Voters in California will choose whether most foods made with genetically modified ingredients should be labelled as such.

How ballot measures work To get an initiative on the ballot, you need to present a petition and get this signed by a certain percentage of the voting population (this varies from state to state). Almost all campaigns use paid staff to collect signatures. 24 states allow initiatives on the ballot.

on the ballot, you need to present a petition and get this signed by a certain percentage of the voting population (this varies from state to state). Almost all campaigns use paid staff to collect signatures. 24 states allow initiatives on the ballot. The popular referendum , also known as "the people's veto" is another form of ballot measure. This stops legislation in its tracks

, also known as "the people's veto" is another form of ballot measure. This stops legislation in its tracks Sometimes the state is required by its constitution to put an amendment to the public vote. This is called a legislative referendum

Prop 37 is one of the most hotly contested ballot initiatives, with more than $50m (£30m) spent on campaigning - the vast majority of it against GM labelling, and coming from large agribusiness companies.

Those in favour say the public has a right to be informed on what they eat, and point out that over 50 countries around the world already have similar labelling.

Opponents say it would lead to higher food prices, and that labelling GM food would give consumers the false impression that it unsafe to eat.

Eighteen states in the US have tried to introduce GM labelling in the past, but all attempts have failed.

Over one million signatures were gathered in California to get this on the ballot and it is the most talked about of all the state's initiatives, says Thad Kousser, a politics professor at the University of California at San Diego.

"It's going to be very close," he predicts, and if it passes it could set a trend for the rest of the country.

4. Death penalty

California is set to vote on a proposal to eliminate the death penalty, and replace it with life imprisonment without parole.

Ballots of the past Looking through past ballot questions is "almost like a window into American history," says Jennie Drage Bowser, citing women's suffrage and prohibition of alcohol as examples. There was a time in the 1940s when dairy farmers wanted margarine banned, she says. Ballots can have "a huge impact" on people's lives. Database of all ballot questions

There are currently 725 inmates on death row in California (more than any other state) and - if the measure is passed - their sentences would be converted to life imprisonment.

The proposal would require prisoners to work in prison, with some of this money going to victims. Supporters of Prop 34 say it would save California money, because the cost of appeals over death sentence cases is so high.

Opponents say the death penalty is the correct punishment for certain crimes, and they dispute those figures.

"It's a huge issue in California politics," says Kousser, and polls suggest voters may come down in favour of abolishing the death penalty.

But, he says, it has received relatively little attention because there is no big money backing either side.

5. Abortion

This is one of those "perennial" issues on the ballot, says Jennie Drage Bowser. Since the 1970s, there have been 37 ballot measures on abortion.

Big bucks The ballot initiative system was designed in the early 1900s as a kind of direct democracy, because local government was seen as corrupt, says Jennie Drage Bowser. But it didn't take long for money to become an important part of the initiative process itself

"Money helps, but it doesn't dictate outcomes," says Thad Kousser, who estimates that it takes around $2m (£1.2m) to get an initiative on the ballot. Campaigning costs are on top.

This year in Montana, voters will decide whether parents must be notified when a girl under 16 plans to have an abortion (this is the case in the majority of US states).

Proponents say an abortion is a serious operation that should not be left to someone under 16 to decide, and that parents have a right to be informed.

Opponents say if a young girl has been the victim of sexual abuse at home, parental notification could put her in danger.

In Florida, voters will decide whether to ban the use of state funds for abortions (except in cases of rape, incest and danger to the mother).

If passed, the ban would mean state employees would not be able to use their health insurance programmes to cover abortions.

6. Fluoride

People in the city of Wichita in Kansas, will vote on a proposal to add fluoride to the city's water.

Proponents say it is a cheap and effective way of reducing tooth decay, has been used for decades in the US, and has been endorsed by the Centers for Disease Control and Prevention.

Opponents see it as a kind of forced medication, and say that adding fluoride to drinking water amounts to undue government intervention, takes away choice, and benefits the fluoride industry.

Wichita rejected fluoride in a referendum in 1964, and it remains a hot issue today, says Ken Ciboksi, professor of political science at Wichita State University.

"It will be a magnet for getting people to the polls. People feel very intensely about the issue." He predicts fluoride will be rejected again: "American individualism is playing out here pretty strong."

Fluoride in water has proved a controversial issue in the UK too.

7. Renewables

A minimum of 25% of Michigan's electricity would have to come from renewable sources by 2025 if voters opt in favour of a ballot proposal there.

If passed, it would require a constitutional amendment and would make Michigan the the first state in the US to enshrine a minimum level for renewables within its constitution.

Supporters say it would make Michigan a hub for the green energy industry, and create thousands of new jobs.

Opponents - including large energy companies and businesses - say energy prices would rise, and that, as a constitutional amendment, it would be very hard to reverse or amend.

8. Assisted suicide

Massachusetts voters will decide on a proposal to allow doctors to prescribe medication to end the life of a terminally-ill patient, where the person has less than six months left to live, is in a fit condition to make a choice and has expressed a wish to die.

Proponents say it is about allowing a person to die with dignity.

Opponents say it is wrong to help end a person's life, and that there are not enough safeguards in place.

Polls suggest the measure is likely to pass. Oregon approved a similar law 15 years ago, as did the state of Washington in 2008.

9. Bridge to Canada

There has been huge controversy over a new bridge on one of the busiest trade routes between the US and Canada.

The Canadian government supports the new bridge linking Detroit in Michigan to Windsor, saying the current one regularly gets congested and will not meet future demand.

Under a deal reached in June, it even agreed to fund it upfront.

The new bridge is supported by the Republican governor of Michigan, Rick Snyder, and many businesses.

Opposition is led by the Manuel "Matty" Maroun, the billionaire owner of the existing bridge covering the same route.

He has spent millions on a ballot initiative that would also require all international bridges in the state, including this one, to be approved by referendum.

10. Casinos

Gambling used to be frowned upon in the US and tightly regulated, but there has been "a tremendous expansion" in the last 30 years, says Prof Melissa S Kearney, an economist at the University of Maryland.

Career moves A ballot initiative can be a useful step into politics. Movie star Arnold Schwarzenegger's Prop 49 - on grants for after-school programmes in California - really put him on the political map in 2002

It is now a "relatively easy way" for a state to raise extra revenue, and is far less controversial than proposing tax increases.

This year, voters in Maryland are being asked if they want to expand gambling in the state - allowing table games like poker for the first time, as well as authorising a new casino.

The money would go to funding education, say proponents.

Critics point to studies which show an increase in crime around casinos.

Voters in Oregon will be asked whether they want to lift the ban on casinos in the state (at the moment, the only casinos which can operate there are on Native American land).

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