The Ballymena, Cushendall and Red Bay Railway ran north-eastwards through the glens of County Antrim. It was opened as a narrow-gauge mineral line in 1875 to exploit the extensive ironstone deposits in the hills inland from the coast. Several mineral branches were developed from the main BC&RBR route, especially at Cargan, some being of considerable length stretching out to the adits dug into the hillside.

The line reached its summit of 1,045 feet just before its terminus at Retreat. Despite plans for additional lines near the Ballymena end, the BC&RB was never a particularly profitable concern and, in 1884, it was taken over by the Belfast & Northern Counties Railway of Ireland. By 1888 the B&NCR had introduced passenger services over what had previously been a freight-only line in an effort to stimulate tourism and day-tripper traffic to this very scenic part of Ireland, as well as local passenger bookings. This service operated between Ballymena, where it connected with the B&NCR standard-gauge (Ireland) services to Coleraine, Portrush and Derry, and Parkmore station high up in the glens and relatively convenient to the scenic Glenariff.

Originally, it had been intended to continue the line beyond Retreat, down the glenside to Red Bay for the export of ironstone but this would have required a railway which would have competed with Switzerland's most dramatic mountain lines with regard to gradient. Consequently, ironstone ore travelled away from the coast inland to Ballymena where it was either transhipped onto standard-gauge wagons for transfer to the ports of Larne or Belfast, or, subsequently continued on the B&NCR-owned Ballymena & Larne narrow-gauge line to the latter port.

In the 1920s the parent company was absorbed by the London, Midland and Scottish Railway which administered its lines in Ireland through its Northern Counties Committee. The BC&RB was one of these lines. It was extensively refurbished and re-equipped in an effort to prolong its life as a primarily passenger and tourist line but falling receipts and rising costs brought about its closure in 1940. Perhaps the regular running of mixed passenger and freight trains, with passengers waiting on the shunting of goods wagons, did much to undermine both punctuality and convenience for the average traveller.

The BC&RB was steam-hauled throughout its life. Some of its rolling stock was moved to other lines or bought by other companies but, unfortunately, nothing survived into preservation. Photos of the line are quite rare, especially in its pre-LMS(NCC) days. Today, much of the course of the line is still visible and makes an excellent path through what remains a beautiful, tranquil and relatively unspoiled part of north-east Ireland.

The standard account of the line can be found in The Ballymena Lines by E M Patterson (Newton Abbot, 1968). This has recently been enlarged and reissued by Colourpoint as The Mid-Antrim Narrow Gauge (Newtownards, 2007).