Railways in Britain were nationalised under the terms of the Transport Act 1947 which came into effect on 1 January 1948. The Railway Executive, a corporate body subordinate to the British Transport Commission, was created to manage and operate the railways. It divided them into six geographical regions, largely based on the areas served by the pre-nationalisation railway companies. Between 1948 and 1998 the creation of Scotland’s railway system was under a unified system of management, for the first time, as a complete administrative unit it its own right, but also as part of the nationalized system for the whole of the United Kingdom.

Between 1948 and 1952 the Chief Regional Officer of the Scottish Region (ScR) was responsible to the Railway Executive for day to day operations in his region. After the Railway Executive was abolished in 1952, he reported to the British Transport Commission (BTC). In 1963, the BTC itself was abolished and replaced by British Railways Board (BRB). Between 1963 and 1968 the Scottish Region was a statutory board in accordance with the provisions of the Transport Act 1962, subordinate to and reporting to BRB. In 1958 James Ness became the General Manager of the Scottish Region, in 1967 Thomas Forbes Cameron was the Chief Regional Officer (CRO), in 1979 Chris Green was the Chief Operating Manager (COM) and then promoted to General Manager in 1984 and in 1986 J. Cornell became the General Manager of ScotRail (the General Manager is a senior postion to the CRO and the COM). It was the first region to adopt a two-tier management structure in 1966, eliminating the divisional level from most functions. In the two-tier system the area managers and area maintenance engineers report directly to senior managers at Regional headquarters in Glasgow.

The Region differentiated from the other five regions by the variety of shipping, hosting five of the highest railway summits, two underground railways with steam power and not one mile of the British Rail ScR was electrified. Railway-owned ships in Scotland became the responsibility of the Railway Executive. The ScR's main routes were Burnmouth and north on the East Coast Main Line, Caledonian, Callander & Oban Lines, Inverness to Wick and the Waverley line. With 3,625 miles of route, the new ScR was almost the same size as the Western Region representing 19% of total British Rail (BR) mileage. The two main constituents of the BR ScR were the former London Midland and Scottish Railway (LMS) and London North Eastern Railway (LNER) networks north of the Border. The ScR had boundaries with the North Eastern Region near Berwick-upon-Tweed and the London Midland Region near Gretna.

Following the Modernisation plan in 1955, the suburban Glasgow lines were electrified in 1956 and electric power was extended to reach Glasgow in 1974 expanding the Glasgow suburban network. Three years after the programme of electrification, with poor investment, the region had to reintroduce steam on the Glasgow to Aberdeen services. During the mid 1960s many routes were closed under the "Beeching Axe", plus some after the resignation of Dr Richard Beeching - most notoriously the Waverley Line from Edinburgh to Carlisle. Lines proposed for closure in the Beeching Report, but which escaped the axe and remain open to this day are Inverness to Kyle of Lochalsh, Wick and Thurso and Ayr to Stranraer. In 1974 cross-border electric Inter-City services from Glasgow Central to London Euston commenced, with the completion of the West Coast Main Line electrification project. In 1979 the Argyle Line project saw the reopening and electrification of the railway line through Glasgow Central Low Level station. The Glasgow Central to Ayr line was electrified in 1986. The one closure of this period was the Kilmacolm line in 1983.

The region ceased to be an operating unit in its own right in the 1980s and was wound-up at the end of 1992, this was caused by BR reorganising the regional structure to be abolished and replaced with business-led sectors. In 1992 Railtrack acquired the track. This process, known as ‘sectorisation’, led to far greater customer focus, this was cut short in 1994 when privatisation caused BR to split up. This sectorisation meant that the last remaining territorial unit from the regional system was ‘ScotRail’ which was a blend of sector and regional management, with a single director covering a dual role. The ScotRail brand was created by BR ScR manager Chris Green in 1983 to provide a distinctive brand for the BR network in Scotland. The brand was adopted by National Express when it took over the franchise from British Railways during privatisation in 1997.

With the privatisation of BR the railway infrastructure of the ScR came under the Scotland Zone of Railtrack. Passenger services within Scotland were franchised to National Express, under the name "ScotRail Railways", although it was still referred to as ScotRail, the name that the BRB used in its later years of operation.