The first railway promoted entirely from within Cumbria, the Maryport & Carlisle (M&C) extended little beyond its original concept, and retained its independence until 1923 as the oldest company to become part of the London Midland & Scottish Railway. The initiative came from local landowners anxious to open up the northern part of the West Cumberland coalfield, and to develop the harbour at Maryport for the shipment of coal to Ireland and the Isle of Man. An added bonus would be the cross-country link-up with the Newcastle & Carlisle Railway.

The line was opened in stages between 1840 and 1845 and, after a shaky start, temporarily becoming part of George Hudson's empire at the end of the 1840s. The 1850s, however, saw the company establishing a firm basis for its future prosperity, especially after the arrival of John Addison as secretary in 1858. By 1873 dividends reached 13% as the line realised its true potential, not only as a local coal carrier, but as a vital link between the iron and steel industry of West Cumberland and the rest of the national railway system. Only once in the rest of the company's existence did the annual dividend to shareholders fall below 5%.

The M&C was not without its challengers: several times it discussed possible mergers with other companies, from the N&CR in the early days, through the LNWR to the Cleator & Workington Junction and Furness Railways before the First World War.

Proposals by the Silloth Railway & Dock Company to break the M&C's monopoly in the Aspatria coalfield led to the opening of the Mealsgate branch in 1866 to be followed the next year by the Derwent branch to Brigham, giving a link to Cockermouth and Whitehaven Cleator & Egremont Railway using running powers on the Cockermouth & Workington Railway. During the 1860s the Solway Junction Railway threatened to completely bypass the M&C in the carriage of iron ore to Scotland and the Cleator & Workington repeated this threat in the 1880s.

Although most of its local stations are now closed, the M&C line continues to provide the rail link between West Cumbria and the rest of the rail network, though the heavy freight traffic at one time generated by the steel and chemical industries has been greatly reduced in recent years.

The M&C pursued a very independent locomotive policy. In 1922 it had 33 locomotives of which 21 had been built in the company's own workshops at Maryport. Only three new locomotives were added to stock in the last 22 years, though many others were very substantially rebuilt during the same period. After the 1923 grouping the drive to standardisation on the LMS ensured the small classes and individual locomotives soon disappeared. By end of 1930 only eight remained, and all were gone by the end of 1934.

See also The Maryport & Carlisle Railway in 1921, extracts from The Railway Year Book.