It was conceived as the Dundalk and Greenore Railway in the 1860s to provide a link between the towns in its title and the London and North Western Railway port at Greenore, from where a ferry service operated to Holyhead.

Because the partition of Ireland placed an international frontier across the DN&G's Greenore – Newry line, it was not absorbed into either the Great Southern Railways in 1925 or the Ulster Transport Authority in 1948.

The line was closed on 31 December 1951 and was dissolved in 1957 by the British Transport Commission Act 1957 (5 & 6 Eliz.

1 built in 1909, a composite with a coupé compartment, has been preserved at the Ulster Folk and Transport Museum, Cultra.

It is believed that this was because of an ill-informed belief among those in charge of its fate that the locomotive was of a different track gauge to the rest of Ireland, due to the fact that it was built and owned by a British company, although this was not the case.