As a pioneering railway, it adopted a track gauge of 4 ft 6 in, and at first operated as a toll line, allowing independent hauliers to move wagons, using horse traction.

The Wishaw and Coltness Railway opened from 1833, connecting iron pits and works further east to Whifflet (then spelt Whifflat) for access to the Coatbridge ironworks.

The M&KR and the Ballochney companies enjoyed huge commercial success as the iron smelting industry boomed around Coatbridge, and as successful new mineral extraction started around Airdrie, although the Slamannan company's sought-for new mineral business barely materialised.

Their obsolete locomotives, horse haulage by independent hauliers is some parts, the rope-worked inclines and the antiquated operating methods were all considerable disadvantages.

[1] In 1842 the Edinburgh and Glasgow Railway (E&GR) opened its main line (to Haymarket at first) on the standard gauge of 4 ft 8½ in with modern locomotives.

In 1844 the M&KR had built a short spur to transshipment sidings with the E&GR at Garngaber, a little east of the present-day Lenzie station.

Hence locomotives were involved in a ceaseless pattern of stopping and shunting, and averaged only 24 miles per day against the 90 miles normal on the Edinburgh & Glasgow.The sidings were expensive to work, and even private sidings required main line points which had to be renewed every three or four years ... these numerous points also meant the employment of a large number of men to supervise them.

[3]In 1846 it became clear that the E&GR directors favoured a purchase of the coal railways, giving it immediate access to the collieries and ironworks, and gaining possession of the territory against newly promoted lines.

[2] The harbour at Borrowstounness (Bo'ness) was also not far from Causewayend, and a connection to it was desirable, enabling export and coastwise mineral trade.

The unbuilt line was absorbed into the Monkland Railways at the time of formation of that company, but the subscribed capital of £105,000 was to be kept separate.

The approach to Bo'ness Harbour itself was to be along the foreshore there, and the company was obliged to build a promenade on the sea side of the railway line there.

He had obtained a patent for the process in October 1850, and the torbanite had been discovered on the Torbanehill estate, about halfway between Bathgate and Whitburn.

A train of coal wagons passed along the Bathgate branch on 11 June 1855, apparently while the line was still in the possession of the contractors.

The Board of Trade Inspector visited the line in 1856 to review the proposals for passenger operation; he reported that there was no turntable at Bathgate, but that one had been ordered.

He continued: The Bathgate and Bo'ness [routes] form a junction at Blackstone; from thence the traffic of the two branches will be conducted separately along the single line common to both, as far as Avon Bridge, a distance of three-quarters of a mile, then they will be united in one train, and proceed to Glasgow.

[2] The 1853 act also gave authority for a branch from Colliertree, near Rawyards, southwards to Brownsburn, where the Calderbank Iron Works would join it with an internal private railway.

There was immediately a considerable traffic from the mines to the works, and it made a long detour, starting eastwards from Armadale, away from the direction of Calderbank, and then round via Slamannan.

The company observed that the gap of ten miles could be closed relatively cheaply, and a direct line would also connect worthwhile coalfields on the way, as well as the important paper works at Caldercruix.

First was a short westwards extension from Cowdenhead to Standhill Junction, and from there turning back to Craigmill (otherwise known as the Woodend Branch), opened on 1 November 1858, to serve the Coltness Iron Company's mineral workings there.

The first was the gap from Barblues (sometimes spelt Barbleus, near Stepends) to Standhill Junction (near Blackridge; the junction was with the uncompleted Shotts Iron Works line (below), and that was completed by 27 April 1861 when a trial mineral train passed over the line; full opening to mineral trains was about 10 May 1861.

[2] Passenger working between Coatbridge and Bathgate started on 11 August 1862; however there was no direct route to Glasgow yet, except over the former Garnkirk railway Caledonian section.

The larger company used the acquisition to consolidate its dominance of mineral traffic in the Monklands coalfield and in connection with the iron works in the area.

The Monklands section it had acquired was profitable, although its operating costs were very high, and it was concentrated in mining areas generally remote from the large population centres.

Coal extraction continued to flourish in the second half of the nineteenth century, and new pits opened throughout the Monklands area.

Many of these were remote from the network of the Monklands section of the North British Railway, and many private mineral branch lines and tramways were built to close the gaps.

It ran from Kipps via Nettlehole and Greengairs, to join the Slamannan line at Southfield Row, an existing colliery spur south of Longriggend.

However many of the more remote localities were dependent on the mineral activity they served, and after World War I there was some geological exhaustion as well as competition from cheap foreign imports.

As passenger suburban travel in Greater Glasgow experience a revival, a short extension along this line to a Drumgelloch station, on the eastern margin of Airdrie, was electrified and opened, in 1989.

The line onward from Drumgelloch to Bathgate was reopened on 12 December 2010 as an electrified railway with a frequent passenger service between Edinburgh and Glasgow.

The largest section of the Monkland Railways network now in operation is the line between Coatbridge and Bathgate; it carries (2015) a well-patronised fifteen-minute interval passenger service between Helensburgh and Milngavie, and Edinburgh.