The station is near Knockmore Junction, which came into service in 1863 for the Banbridge, Lisburn and Belfast Junction Railway to connect with the Ulster Railway. The junction gained another branch in 1871 when the Dublin and Antrim Junction Railway was opened. The Ulster Railway, BLB and D&A all became part of the GNR by the end of the 1870s. A halt was finally provided at Knockmore Junction in 1932, but it did not last long and was closed a year later. The GNR was nationalised in 1953 as the GNR Board, which closed Banbridge branch on 29 April 1956. In 1960, the Antrim branch was closed to passenger traffic, although it remained open for freight. By this point, the line was under UTA control; All GNR assets in Northern Ireland having been ceded to the UTA in 1958. In 1968, the UTA was replaced by Northern Ireland Railways, which reopened the Antrim branch and rerouted all Londonderry line services via Knockmore. A new Knockmore halt was built on a different site to the original, slightly closer to Lisburn. Instead of using a crossover as per the original setup, a 3rd line was laid directly from the former junction to Lisburn station. Unfortunately, this required the demolition of Knockmore Junction signal cabin. In 2001 NIR reopened the more direct Belfast – Antrim route via. An attempt was made to keep the Antrim – Knockmore line open alongside it using a skeleton service, but this was unsuccessful and NIR withdrew passenger services altogether in 2003. Due to the platform layout, this left Knockmore station with a train service in only one direction: "down" trains from Belfast to Portadown. Unsurprisingly this arrangement was not well-used, and so on 25 March 2005 NIR closed Knockmore station. The Portadown-bound platform was demolished in 2012, with the branch platform following in 2014.
Future
NIR have included in their corporate plans for a new Knockmore park and ride station further down the line called Lisburn West. The station would serve Portadown line trains in both directions, as well as Antrim branch trains if the line is reopened. So far, Translink has bought and demolished the former Lisburn South Eastern Regional College, which is where Lisburn West is to be built.
Incidents
On 28/06/2012, a section of embankment near Knockmore was washed out by heavy rain, leaving a short length of track unsupported in mid-air. Due to the Irish Open, Translink had put on extra trains to Portrush, some of which were scheduled to use the Antrim branch. The first of these specials was not able to stop in time and crossed over the unsupported track, with the leading vehicle coming to a full stop with one bogie on either side of the unsupported section. The train was slowly reversed back to Lisburn station, and nobody was injured.
On 04/02/2016, a Portadown-bound train collided with an excavator bucket which had been left on the track near Knockmore Junction. The leading vehicle was lifted off the rails, coming to a stop 330m from the point of collision with the bucket lodged under the fuel tank, but all wheels on the rails. It was badly damaged and as of August 2016, has not returned to service. One passenger was injured.
