The Isle of Purbeck had been quarrying limestone and digging ball clay long before the Victorians arrived. The Southampton and Dorchester Railway opened through Wareham in 1847, taken over the following year by the London and South Western Railway, but the main line passed several miles north of the mineral workings. For decades, several schemes to connect Swanage to the railway stalled for lack of money. Eventually, on 18 July 1881, a private company called the Swanage Railway obtained an Act of Parliament with £90,000 of share capital. Under the consulting engineer W. R. Galbraith, the branch was built single track from Worgret Junction, west of Wareham, to a new station in Swanage. The line opened on 20 May 1885. The LSWR operated it from the first day. By 1886 the smaller company had been absorbed into the LSWR entirely.

For most of the next eighty-six years the branch carried tourists in summer and Purbeck stone in winter. After British nationalisation in 1948, push-and-pull trains ran the local service, and through carriages sometimes joined from the Weymouth main line. The 1963 Beeching Report did not list the Swanage branch for closure, but the 1960s collapse of rural rail traffic caught up with it anyway. In May 1967 the government announced the line would shut. A Department of the Environment inspector ruled it should stay open, the Secretary of State overruled him, and the line closed to passenger services on 3 January 1972. Freight kept moving for a few more years, then that too stopped. The Swanage Railway Society formed almost immediately. Volunteers fought British Rail through the courts to slow the lifting of the track, then began the slow work of buying it back, foot by foot.

The preserved line reopened in stages from Swanage outwards. By the late 1990s the volunteers had reached Corfe Castle, where the station sits in the shadow of the medieval ruin that dominates the Purbeck Hills, and on to Norden, the modern park-and-ride terminus. Today the heritage railway runs nine and a half miles from Norden through Corfe Castle and Harman's Cross and Herston Halt to Swanage. At summer peak times trains depart every forty minutes, one of the most intensive heritage railway timetables in the country. Steam haulage is the norm. The route undulates with the Purbeck landscape: a ruling gradient of 1 in 76 or 1 in 80, dropping from Worgret Junction, climbing to Furzebrook, falling again to Corfe Castle, climbing once more, and finally descending to the sea at Swanage. Most passengers ride the line for the view of the castle ruins from the carriage windows.

The bigger ambition was always to reconnect Swanage to the national network. In 2007 the permanent track connection to Network Rail at Worgret Junction was used for the first time, allowing diesel locomotives to come through from Eastleigh Works for a gala event. In 2009 the Purbeck Pioneer, a twelve-coach diesel railtour, became the first public train between Wareham and Swanage since 1972, and the Dorset Coast Express ran on steam behind Battle of Britain class locomotive 34067 Tangmere a month later. In 2017, after Dorset County Council and Purbeck District Council put up £3 million for re-signalling at Worgret Junction, the railway launched a two-year trial diesel service between Wareham and Swanage. The work won the Institution of Civil Engineers' South West Engineering Award for 2017. In 2021 the government included the line in its Restoring Your Railway scheme, and in 2023 a four-day-a-week summer service between Wareham and Swanage finally returned.

The railway is also a museum that runs trains. Its Heritage Coach Project is working through eleven historic carriages, four already operational, others awaiting their turn in the Herston works on the outskirts of Swanage. Coach No. 1346, a Maunsell Open Third built by the Southern Railway, returned to traffic in October 2022. The railway has recovered a Victorian stone water tower from Salisbury and is rebuilding it beside Northbrook Road Bridge to feed its steam locomotives from a spring extraction system, sparing the boilers the damage that mains water does. In September 2025, in the week of the bicentenary of the Stockton and Darlington Railway, Historic England gave Grade II listed status to the Swanage loco shed, the turntable pit and retaining wall, and the Northbrook Road overbridge. The railway has become, in the formal sense, a heritage asset.

What started in 1972 as a handful of enthusiasts refusing to let a branch line die has become an operating Victorian railway in twenty-first-century England, owned by a charitable trust, staffed largely by volunteers, used by over 200,000 passengers a year. Children press their noses to the windows as the train rounds the curve below Corfe Castle. Steam drifts across the platform at Norden as the locomotive runs round its train. Whistles echo off the chalk hills. The line carries a fragment of working railway history into the present, and from May to October it carries it the full way back to the main line at Wareham, just as the original Victorian directors intended.