To some it's just a line on a map - but to many others the border is a burning issue.
Its influence isn't just felt in politics, but in the economy, education, health and even sport.
In theory, under the terms of the Good Friday Agreement, a referendum could be held once every seven years, and in the next few days Sinn Féin is expected to ratchet up its campaign for one.
But is there real support for such a move?
"I suppose Sinn Féin has to be doing something about the Irish dimension, as we used to call it, and promoting or calling for a border poll is one way of expressing to their own followers their continuing commitment to a united Ireland," said author and journalist Eamonn McCann.
"I think a Border poll would literally be a flag-waving exercise, as you would see political parties on each side of the communal divide identifying themselves, they would march into political battle on a border referendum carrying their particular flags. Do we really want that?"
A referendum rejected a united Ireland in 1973. Now 40 years on, and with tensions over flags still polarising communities, it's still hard to sell the proposition to unionists.
The recent census provided interesting reading for those looking for twitches on the web of Northern Ireland society.
There is this evolving Northern Irish identity where many people feel safe and content to call themselves Northern Irish and they want to focus on how Northern Ireland can fulfil its potential and how we can create economic stability in Northern Ireland, rather than looking at Irishness or Britishness
Prof. Deirdre Heenan
It showed that attitudes towards identity and nationality are evolving.
Professor Deirdre Heenan said: "I think the recent census took many people by surprise because what it shows is it's no longer correct to talk in terms of a British or an Irish identity, that it's a simple dichotomy between the two."
Tourists may barely notice when they cross the border, but it's not so simple for businesses.
Economic analyst Paul Gosling said: "In Northern Ireland we're a half-way house.
"We're half-way between the Irish Republic and half-way between Great Britain.
"So we haven't got a fair system in terms of competing with the south because of corporation tax, yet we're not integrated with the Great British economy either, so we've got the worst of both worlds.
"But I think the real threat to the economy of Northern Ireland would be if the United Kingdom leaves the European Union, and I think if Northern Ireland, with the rest of the UK, left the European Union that would create enormous problems in terms of separating our economy from the South because in many ways we are integrated now."
Debating the issue on UTV Live Tonight, Sinn Féin TD Pearse Doherty defended the timing of the campaign, amid unrest over the Union flag.
"That shouldn't be an excuse to not pursue a campaign which the majority of people on the island of Ireland would like to see," he explained.
"The majority of people in the island of Ireland want to see Irish reunification but we recognise that the Good Friday Agreement allowed for a border poll and it would be a decision for people within the north.
"This isn't about sectarianism, this is about having a conversation with Unionists.
"This is about allowing people to make their own decision and to have that option of where they would like to see their future lie and what is in the best interests of them economically."
Meanwhile the Enterprise Minister for Enterprise, the DUP's Arlene Foster, described it as a "stunt politics".
She said: "I think very much it is stunt politics because it is very lazy sectarianism to look at the census and say that there has been a change.
"If there has been a change, it is actually the fact that people in the Nationalist community are content in calling themselves Northern Irish and I think that is very significant because people are content in their identity here in Northern Ireland.
"They accept that that is the case and in actual fact a border poll can only take place if the Secretary of State - and Sinn Féin know this, so it is a stunt - it can only take place if the Secretary of State decides that there is evidence to support such a change and there is no such evidence."
While Sinn Féin tries to persuade unionists to hitch their wagon to the United Ireland train, commerce and manufacturing may be keeping a wary eye - not on removing the Irish border, but on whether the UK is likely to resurrect its old borders with the rest of Europe.