The state has often been a bellwether for American politics.
Since 1952, the primary has been a major testing ground for candidates for the Republican and Democratic nominations.
Candidates who do poorly frequently drop out, while lesser-known, underfunded candidates who do well in New Hampshire suddenly become serious contenders, garnering large amounts of media attention and campaign funding.
Only a few delegate votes are at stake but the importance of winning early can never be underrated.
This week, Democrat Bernie Sanders easily trounced Hillary Clinton and bombastic Republican Donald Trump raced ahead of his fellow presidential nominee challengers.
Mr Sanders has proved popular with young voters and women as he espouses his anti-Wall Street message.
He wants to break up the banks and is calling for income equality.
Mr Sanders also appeals to independent voters who, in New Hampshire, are allowed to vote for any candidate.
He serves as an independent in the Senate.
The next primary in South Carolina, where more than half of the Democratic primary voters in 2008 were African American, will be a challenge for Mr Sanders, because of the work former president Bill Clinton carried out in the South.
Mr Sanders met one of American's most prominent civil rights activists, Al Sharpton, just hours after New Hampshire.
The Clintons have a long history of support for civil rights and Mrs Clinton has benefited from her husband's popularity in the black community during his presidency.
But as black and Hispanic voters have become more familiar with Mr Sanders, the more they appear to like him.
The Republican Party is desperate for a moderate candidate to emerge to challenge the growing popularity of Mr Trump.
His victory in New Hampshire, along with that of Mr Sanders, is testament to the large number of Americans upset at US economic conditions and who are prepared to send a shockwave to Washington.
Ohio Governor John Kasich won a spirited fight for second in the Republican field, while US Senator Ted Cruz, of Texas, former Florida governor Jeb Bush and US Senator Marco Rubio fought for third place.
Of the also-rans in New Hampshire, Mr Bush is by far the best resourced with both money and people.
As the campaign heads to Super Tuesday on March 1, where 22 states will cast their primary votes, the Republican organisation will be expecting Mr Bush to have moved up the ladder.
With still so many challengers remaining in the Republican ranks, the votes will be split, allowing Mr Trump to continue bulldozing to the top.
It is different in Democratic circles, as Mr Sanders and Mrs Clinton are the only two remaining.
Both have different political backgrounds.
Mrs Clinton is seen as part of the establishment, accepting generous business backing while criticising Wall Street.
Mr Sanders has a huge network of supporters, who are providing smaller amounts of money individually to provide a large pool of campaign funding.
The win in New Hampshire will mean more larger donations heading his way.
The consolation the losers in New Hampshire can take is from history.
Not every candidate who wins in New Hampshire goes on to win their respective party's nomination.
Mrs Clinton won in 2008 and lost the nomination to Barack Obama, who then became president.
The chances of an establishment-type Bush versus Clinton presidential contest are still live, but so are the chances of a more radical presidential exchange between the Trump and Sanders camps.
The one issue no-one is yet talking about is the possibility of billionaire and former New York mayor Michael Bloomberg entering the race as an independent.
Independents have never done well in previous presidential elections.
But no election has been quite like this.
