Caledonian Railway

During the process of seeking parliamentary authorisation, the Caledonian observed that the Clydesdale Junction Railway was being promoted. The Caledonian acquired that line during its construction, and it opened in 1849. It gave an alternative and shorter access to another Glasgow passenger terminal, named South Side, and to the Clyde quays at General Terminus (over the connected General Terminus and Glasgow Harbour Railway). The South Side station was already being used by the Glasgow, Barrhead and Neilston Direct Railway, worked by the Caledonian. One day, they hoped, they might extend that line into Ayrshire. Meanwhile, the line was leased (for 999 years) to the Caledonian in 1849.

The Caledonian recognised that the Townhead terminus was unsatisfactory and constructed a deviation from Milton Junction to a new Glasgow terminus at Buchanan Street. It opened on 1 November 1849. Trains to Edinburgh, Stirling and Carlisle used the new station; the Stirling trains had to reverse at Gartsherrie Junction. The Garnkirk's old Glebe Street (Townhead) station was reduced to goods and mineral duties. In 1853–54 the Hayhill Fork, between Gartcosh and Garnqueen, was opened, enabling direct running from Buchanan Street towards Stirling.

Financial problems, and Greenock amalgamation

In the period between formation of the Caledonian Railway and the opening of the main line, a large number of leases and working arrangements had been concluded with other railways being promoted or built nearby. This was mostly done by guaranteeing those shareholders an income on their capital, which meant no immediate cash was required. When the lines started working, suddenly a huge periodical payment was required, and the income was inadequate to satisfy it. There were also suggestions of improper share acquisitions, and in the period 1848 to 1850 a number of shareholder inquiries disclosed bad practices, and many board members had to resign in February 1850.

The company had obtained the Caledonian and Glasgow, Paisley and Greenock Railways Amalgamation Act 1847 (10 & 11 Vict. c. clxix) giving it powers to merge with the Glasgow, Paisley and Greenock Railway (GP&GR) in 1847, but even more alarming revelations of financial impropriety emerged regarding that company, and the Caledonian considered getting authorisation to cancel the amalgamation. However, it was later decided to proceed, and the amalgamation took place by the Caledonian Railway Arrangements Act 1851 (14 & 15 Vict. c. cxxxiv) of 7 August 1851. The GP&GR operated the line between Glasgow and Paisley jointly with the Glasgow and South Western Railway (G&SWR), and the Paisley line used a terminus at Bridge Street in Glasgow.

The Caledonian now worked trains at three termini in Glasgow: Buchanan Street, South Side (from the Clydesdale Junction line, mostly used for local trains to Motherwell and Hamilton), and Bridge Street (on the Paisley line).

Gradually the financial difficulties were got under control, by economy, and by the discovery that several of the lease agreements were illegal. Handsome dividends continued to be paid, but it was not until March 1853 that the dividend was paid wholly from revenue.

South Lanarkshire: mainly mineral traffic

If the Caledonian Railway had been formed as an intercity trunk line, its attention was early on turned to other demands. Local interests in Lanark promoted a branch line to their town, opening in 1855. Coal owners in South Lanarkshire pressed for a railway connection, and the Lesmahagow Railway was formed by them, opening in 1856. It was later absorbed by the Caledonian, but other lines followed in the sparsely populated but mineral-rich area. As new coal mines opened, so new branches were needed, connecting Coalburn, Stonehouse, Strathaven, Muirkirk and Darvel and many other places, with new lines built right up until 1905. When the coal became exhausted in the second half of the 20th century, the railways were progressively closed; passenger traffic had always been light and it too disappeared. Only the passenger traffic to the Lanark and Larkhall branches remain in operation.

North Lanarkshire

In North Lanarkshire, the North British Railway was a keen competitor, having taken over the Monkland Railways. The area contained the rapidly-growing iron production area surrounding Coatbridge, and servicing that industry with coal and iron ore, and transport to local and more distant metal processing locations, dominated the Caledonian's activity in the region. The Rutherglen and Coatbridge line, later linking Airdrie, and the Carfin to Midcalder line were routes with significant passenger traffic. Many lines to coal and iron ore pits further east were built, but serving remote areas the lines closed when the mineral extraction ceased.

The North British Railway (NBR) opened its branch line to Dolphinton, east of Carstairs, and the Caledonian feared that the next step would be an incursion by the NBR into Caledonian territory, possibly seeking running powers on the main line. To head this off, the Caledonian built its own Dolphinton branch from Carstairs; authorised by the Caledonian Railway (Carstairs and Dolphinton Branch) Act 1863 (26 & 27 Vict. c. xxiv), it opened in 1867. Dolphinton had a population of 260 and two railways, and traffic was correspondingly meagre, and the line closed in 1945 to passengers and in 1950 to goods.

The independent Solway Junction Railway was opened in 1869, linking iron mines in Cumberland with the Caledonian Railway at Kirtlebridge, crossing the Solway Firth by a 1,940 yd (1,770 m) viaduct; the company worked the line itself. It considerably shortened the route to the Lanarkshire ironworks, and was heavily used at first, but the traffic was depleted by cheap imported iron ore within a decade. The Scottish part of the line was acquired by the Caledonian Railway in 1873, and the whole line in 1895. Serious ice damage and later heavy maintenance costs made the line seriously unprofitable and it was closed in 1921.

Extending the network after 1880

Moffat Railway

The Moffat Railway was opened from Beattock on 2 April 1883. It was just over 1+1⁄2 miles (2.4 km) long. It was worked by the Caledonian and absorbed on 11 November 1889 under the Caledonian Railway Act 1889 (52 & 53 Vict. c. xii). The Caledonian Railway sought to develop both Moffat and Peebles as watering places, and ran The Tinto Express from both places, combining at Symington, to Edinburgh and Glasgow for several years.

With the intention of revitalising the lead mining industry, the Leadhills and Wanlockhead Branch was opened as a light railway from Elvanfoot in 1901–02. With challenging gradients to reach Scotland's highest village in otherwise remote territory, the line scraped a bare living and closed in 1938.

From Greenock to the Firth of Clyde

In the mid-1850s the steamer connections on the Firth of Clyde assumed ever increasing importance, and journey transit times from settlements in Argyll and the islands to Glasgow became critical. The inconvenient situation of the Greenock station and pier encouraged thoughts of more convenient routes, and in 1862 the Greenock and Wemyss Bay Railway was authorised. It was an independent company intending to provide a fast connection from Rothesay on the Isle of Bute; it opened on 13 May 1865 and in August 1893 it amalgamated with the Caledonian Railway, having been operated by the Caledonian Railway since its opening.

In 1889 the Caledonian itself opened an extension line from Greenock to Gourock, more conveniently situated than Greenock; this involved the expensive construction of Newton Street Tunnel, the longest in Scotland.

In competing with rival rail and steamer connections, the Caledonian became frustrated with its reliance on independent steamer operators, and tried to obtain powers to operate the vessels directly; this was refused by Parliament on competition grounds, and in reaction the company founded the nominally independent Caledonian Steam Packet Company (CSPC) in 1889. The CSPC expanded its routes and services considerably; following nationalisation of the railways in 1948 it became owned by British Railways, but was divested in 1968 and later became a constituent of Caledonian MacBrayne (CalMac), which remains in state ownership.

Glasgow and Paisley suburban lines

In the final decades of the 19th century, as the cities spread into conurbations, the company's attention turned to increasing traffic in areas now thought of as "suburban". Street running tramways were already responding to the demand for passenger travel in these areas, but as yet they used horse traction.

The Cathcart District Railway was promoted as an independent concern but heavily supported by the Caledonian. It opened in 1886 from Pollokshields to Mount Florida and Cathcart (the eastern arm of the present-day Cathcart Circle Line) in 1886, and was extended via Shawlands to form a loop in 1894. It was worked by the Caledonian, although the company retained its independence until 1923.

The Glasgow Central Railway was authorised as an independent company to build a surface line from Rutherglen to Maryhill. It encountered fierce opposition, and the scheme was taken over by the Caledonian and converted into a route mainly in tunnel under Argyle Street. It opened in 1896, further encouraging suburban passenger travel. It closed in 1959 but reopened (as the Argyle Line) in 1979.

The Paisley and Barrhead District Railway was incorporated in 1897 and transferred to the Caledonian in 1902; it was to link Paisley and Barrhead and enable a circular service from Glasgow. The line was substantially ready in 1902 but by now street tramways were electrically operated and eminently successful. It was plain that a passenger service would not be viable against tram competition and the intended passenger service was never started.

North Clydeside

The area of the north bank of the river Clyde became increasingly important for industry, and therefore became heavily populated. The North British Railway and its satellites had gained an early monopoly of this traffic, but its importance encouraged the Caledonian to enter the area.

The Lanarkshire and Dumbartonshire Railway was nominally independent, running from near Maryhill to Dumbarton, opening progressively between 1894 and 1896. In 1896 the Caledonian gained access to Loch Lomond with the opening of the Dumbarton and Balloch Joint Railway (originally built by the Caledonian and Dumbartonshire Junction Railway), built jointly with the NBR.

The Lanarkshire and Ayrshire Railway

In 1888 the Lanarkshire and Ayrshire Railway opened a 6+1⁄2-mile (10.5 km) line from Giffen on the Glasgow, Barrhead and Kilmarnock Joint Railway to Ardrossan. Its purpose was to shorten the route for Caledonian mineral traffic, and it was worked by the Caledonian. In 1903–04 it was extended eastwards to Cathcart and Newton, enabling the heavy mineral trains to avoid the joint line and the congested area around Gushetfaulds from the Lanarkshire coalfields to Ardrossan Harbour.