As the date of the United Kingdom's exit from the European Union approaches without a final agreement, the question remains over what will happen at the border between Northern Ireland and the Republic of Ireland.

There are currently no official passport checks between Northern Ireland, which is part of the U.K., and the Republic of Ireland, which is part of the E.U. Once the U.K. officially leaves the E.U. at the end of March, the 499-kilometer border between Northern Ireland and the Republic of Ireland will become an external border of the E.U.

Residents have reflected on the state of the border during "the Troubles," a period of political unrest and violence in Northern Ireland during the late 20th century. The conflict officially ended with the Belfast or Good Friday Agreement in 1998, rendering the border between the nations invisible. While nothing is decided yet, residents of the area fear the effects the return of a hard border could have on their lives and businesses.

The remains of a railway bridge between the villages of Blacklion in the Republic of Ireland and Belcoo in Northern Ireland can be seen on February 22nd, 2019, in Belcoo, Northern Ireland. The bridge was blown up by the British army in the 1970s during the Troubles. Along the winding 499 kilometers of the Irish border are vestiges of a harder boundary: derelict customs houses, "dragon's teeth" bollards and two-toned tarmac. These relics evoke a time when movement between the countries was less free, and underscore what is at stake as the U.K. negotiates its exit from the E.U. Both parties have vowed to avoid a physical border, but, as the Brexit deadline approaches on March 29th, a final agreement has so far eluded them. (Photo: Charles McQuillan/Getty Images)

Stella Lynne and William Andrews pose for a photograph as they take part in the weekly market that takes place on the Irish border on February 17th, 2019, in County Fermanagh, Northern Ireland. The couple, who are Democratic Unionist Party voters, voted to remain in the E.U. Referendum in 2016 and now fear the return of a hard border. "It looks like the border is coming back, which won't be good," they said. "We've already started to gather tinned food just in case." (Photo: Charles McQuillan/Getty Images)

Julie Taylor feeds her donkeys along the Irish border on February 15th, 2019, in Muff, Ireland. Taylor, who lives on the northern side of the border in nearby Londonderry travels the short distance into Ireland to attend to her animals. She says if a hard border returns, "They don't have the manpower to control a border." (Photo: Charles McQuillan/Getty Images)

Denny Johnston (right) poses for a photograph alongside John Taylor (left) as he trades from the back of his trailer on the Irish border at the Mullan roadside market on February 17th, 2019, in Mullan, Northern Ireland. Johnston, who buys and sells his goods on both sides of the border, fears for his business if a hard border returns. (Photo: Charles McQuillan/Getty Images)

A Border Communities Against Brexit sign can be seen on Aghalane Bridge on February 17th, 2019, in Aghalane, Ireland. Britain will leave the E.U. on March 29th following the referendum in 2016. Many people in Northern Ireland and Ireland are concerned about a return of a so-called hard border, which could inspire unrest reminiscent of the Troubles. (Photo: Charles McQuillan/Getty Images)

The Culicagh mountain boardwalk, which threads along the border between Northern Ireland and the Republic of Ireland, is pictured on February 22nd, 2019, in Florencecourt, Northern Ireland. (Photo: Charles McQuillan/Getty Images)

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