population centres. However the best of the mineral deposits had been worked out, and the focus of the extractive industries had shifted into Caledonian Railway territory. The North British Railway set about rectifying the lack of good connection to Glasgow, and in 1871 the Coatbridge to Glasgow line was opened, from Whifflet. For the time being the Glasgow terminal was inconveniently located at College, later High Street, but the growth of daily travel to work by suburban train motivated the NBR to work towards a better network in the city. The Airdrie terminal of the Ballochney Railway (Hallcraig Street) was closed to passengers in 1870. North Monkland Railway 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. Quarrying was also an important activity. A new railway was promoted to reach some of the pits and quarries north of the Ballochney and Slamannan lines, and the North Monkland Railway got an authorising Act of Parliament on 18 July 1872. The line was opened on 18 February 1878, and carried goods and mineral traffic only. It ran from Kipps via Nettlehole and Greengairs, to join the Slamannan line at Southfield Row, an existing colliery spur south of Longriggend. It connected into numerous collieries on the route, and many short mineral lines were built off the main line to connect the pits. The line sold itself to the North British Railway effective from 31 July 1888, the £10 shares being bought out at £6 each. The twentieth century The Monkland Railways were now just a network of branches of the North British Railway, concentrating on serving collieries and ironworks, and the communities that built up around them. The through Bathgate - Airdrie - Coatbridge line became an important secondary line for passengers and freight. 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. This intensified after World War II, by which time the North British Railway had formed a constituent of the London and North Eastern Railway in 1923, and then been nationalised into the Scottish