The Midland Great Western Railway opened the Ballaghaderreen branch in 1874. The financing arrangements turned out to be brutal for the original shareholders. When the accounts were eventually settled, 13,300 pounds went to the Board of Works to repay the construction loan, and the remaining balance went to the Consett Iron Company, which had supplied much of the iron - leaving the original investors with nothing. This was not unusual in the Victorian railway boom: ambitious local promoters often found themselves bankrupted by the practical economics of branch lines that served small populations. In 1924, the MGWR was absorbed into the Great Southern Railway, which became the Great Southern Railways the following year. The branch survived the merger, though it operated through the early 20th century with the precarious finances that all minor lines suffered. In 1944, an Irish parliamentary debate noted that the line had closed but had been reopened at the request of a member of the house - a glimpse of how political pressure kept rural railways running long past the point of economic viability.

The branch left the main Dublin-Sligo line at milepost 112 and a half, at Kilfree Junction, with its own platform. Freight trains arriving from Sligo could enter the branch without having to reverse. From the junction the line curved off on an embankment and dropped steeply down to milepost 2. From there to milepost 5 the track ran above Lough Gara, with sweeping views to the south-east of one of the great lakes of the region, dotted with crannogs and lined with sedge. Island Road Station - opened in 1909, serving the village of Monasteraden - sat at the five-mile mark. Edmondstown Station was reached at milepost 6 and three-quarters. After Edmondstown the line crossed what railwaymen called "wild boggy country" until reaching the terminus at Ballaghaderreen at 9.75 miles. The crossing of the bog was always the engineering challenge: peat heaves, water tables that move with the seasons, the chronic tendency of any embankment over bog to sink slowly into the soft ground beneath it.

Different classes of steam engine pulled the line over the decades. Up to the 1940s, the J26 0-6-0 tank engines of the MGWR Class E (renumbered GSR 551 Class after the 1925 merger) were the regular workhorses. In the 1950s, the G2 2-4-0 tender engines of the MGWR Class K - GSR 650 Class - took over, with locomotives numbered 666 and 667 typically used in rotation. From about 1955 until closure, the J18 0-6-0 of the MGWR Classes L and Lm (GSR 573 Class) was the designated locomotive. In the line's final years, special trains and freight were sometimes operated by diesel - which is why locomotive B133, a diesel, hauled the cattle special on the final day. The pattern of engine succession is the kind of detail that railway enthusiasts treasure and that nobody else notices: the steady evolution from small Victorian locomotives to the slightly larger and more efficient classes that succeeded them, all of them grinding through the same boggy ten miles.

In the parliamentary record for 21 June 1944, in a debate ostensibly about the Portlaoighise-Mountmellick Railway, a member of the Dail noted that the Ballaghaderreen branch had closed but had been reopened on the behest of another member of the house. The reference is offhand but revealing. Wartime Ireland was struggling with fuel rationing, transport shortages and the practical difficulties of running an isolated neutral economy. Reopening a small branch line during such a period required either a serious economic justification - which the line did not really have - or political pressure from a TD who could deliver. The line ran on through the rest of the war and into the post-war era, but the writing was on the wall. By the early 1960s, road haulage was outcompeting rail for the local freight that had been the branch's economic mainstay. Closure was, in the end, only a matter of timing.

The Ballaghaderreen Chamber of Commerce has proposed converting the old line into a community greenway - a walking and cycling route that would run along the old trackbed from Kilfree Junction to Ballaghaderreen, passing the disused station at Monasteraden and the dramatic views over Lough Gara. The proposal is part of a broader Irish trend that has seen successful greenway conversions on the Westport-Achill line, the Great Western Greenway and elsewhere, drawing significant tourism into rural areas that had lost their railways in the 1960s and 70s. Whether the Ballaghaderreen route will be built remains to be seen - greenway funding is competitive, and many proposals are in the queue - but the local commitment is real. In 2009, pupils of St. Aidan's National School in Monasteraden produced a 32-minute film called The Train, weaving rare archival footage with interviews of older residents who remembered the branch. The branch line still has a community that misses it.