The Company was founded at a public meeting in Bristol in 1833. Isambard Kingdom Brunel was appointed as engineer at the age of 27, and made two controversial decisions: to use a broad gauge of seven feet (actually 7ft 0.25in or 2140mm) for the track, which he believed would offer superior running at high speeds; and to take a route which passed north of the Marlborough Downs, an area with no significant towns, though it did offer potential connections to Oxford and Gloucester.
The company received its Parliamentary Act in 1835, and the first stretch of line, from London Paddington to Taplow near Maidenhead opened in 1838. The full line to Bristol Temple Meads opened on completion of the Box Tunnel in 1841. The initial group of locomotives ordered by Brunel to his own specifications proved unsatisfactory, and 20-year-old Daniel Gooch was appointed as Superintendent of Locomotives. Brunel and Gooch chose to locate their locomotive works at the village of Swindon, at the point where the gradual ascent from London turned into the steeper descent to the Avon valley at Bath.
Various other railways were built in the area to connect with the GWR: The Bristol and Exeter Railway reached Exeter by 1844, The Cheltenham and Great Western Union Railway linked Swindon to Gloucester and Cheltenham in 1845, and the Bristol and Gloucester Railway brought the broad gauge to Gloucester in 1844. Gloucester was already(?) served by the standard gauge Birmingham and Gloucester Railway, resulting in a "break of gauge", and the need for all passengers and goods travelling beyond Gloucester to change trains. This was the beginning of the "gauge war", and resulted in the appointment by Parliament of a Gauge Commission, which duly recommended in favour of the standard gauge.
The undaunted GWR pressed ahead into the West Midlands, in hard-fought competition with the London and North Western Railway. Birmingham was reached in 1852, at Snow Hill (although the GWR had initially meant to build to Rugby instead of Birmingham), and Birkenhead (on standard gauge track) in 1854. The Bristol and Gloucester had been bought by the Midland Railway in 1846 and converted to standard gauge in 1854, bringing mixed gauge track (with three rails so that both broad and standard gauge trains could run on it) to Bristol. By the 1860s the gauge war was lost; with the merger of the standard-gauge West Midlands Railway into the GWR in 1861 mixed gauge came to Paddington, and by 1869 there was no broad gauge track north of Oxford.
Meanwhile, further developments were made in the GWR's heartland: The South Devon Railway was opened in 1849, extending the broad gauge to Plymouth, and the Cornwall Railway took it over the Royal Albert Bridge and into Cornwall, reaching Penzance by 1867. The South Wales Railway opened in 1850 and was connected to the GWR via Brunel's ungainly Wye bridge in 1852. The route from Wales to London via Gloucester was roundabout, so work on the Severn Tunnel began in 1873, but unexpected underwater springs slowed the work down and prevented its opening until 1886.
Through this period the conversion to standard gauge continued, with mixed gauge track reaching Exeter in 1876. By this time most conversions were bypassing mixed gauge and going directly from broad to standard. The final stretch of broad gauge was converted to standard in a single weekend in May 1892. The 1890s also saw improvements in service of the generally conservative GWR - restaurant cars, much improved conditions for third class passengers, and steam heating of trains. The company also built new track to shorten its previously circuitous routes. After 1902 G. J. Churchward developed a distinctive style of locomotive in 4-4-0 and later 4-6-0 configuration, with flat-topped Belpaire fireboxes, tapered boilers, long smokeboxes and much standardisation of parts. These were the Star class locomotives. A notable locomotive (not of the Star class), was 111 The Great Bear, the first 4-6-2 locomotive in the United Kingdom.
At the outbreak of World War I the GWR, along with the other major railways, was taken into government control. After the war the government considered permanent nationalisation, but preferred a compulsory amalgamation of the railways into four large groups. The GWR alone preserved its identity through the grouping, which took effect on January 1, 1923. It subsumed many smaller companies, mostly handling South Wales coal traffic. Though this appeared to be a great coup for the GWR, the coal traffic declined significantly as the use of coal as a naval fuel declined, and within a decade the GWR was itself the largest single user of Welsh coal. The 1920s also saw the introduction of the GWR's most famous locomotives - the Castle and King classes developed by Churchward's successor, C. B. Collett . The 1930s brought hard times, and the records set by the Castles and Kings were surpassed by other companies, but the company remained in relatively good financial health despite the Depression.
World War II brought a further period of direct government control, and by its end a Labour government was in power and planning to nationalise the railways. The GWR became part of British Railways on January 1, 1948. On privatisation the "Great Western" name was revived for the Train Operating Company providing passenger services to the West.
See Also: List of British companies