The Big Water of Fleet Viaduct, known locally as "the Big" was part of the railway line known as "the Port Road", linking Stranraer to Dumfries.
In remote countryside to the north of Gatehouse of Fleet, the route spanned Big Water of Fleet by means of a 300-yard viaduct with 20 arches. In 1940 the piers were strengthened with brick encasings preparatory to carrying munitions.
During the Second World War, the port of Cairnryan was purpose-built as No.2 Military Port with three harbour piers and a railway linking it with Stranraer. Millions of tonnes of ordnance and supplies came into the UK, much of it being transported over the viaduct. Then, in 1943, the railway also helped to move US troops.
The line failed to survive Dr. Beeching's cuts, closing on 14th June 1965. The viaduct's smaller 9-arch sister - Little Water of Fleet - was blown up by the Army as part of a training exercise.
In 1935, the Big reputedly starred in Alfred Hitchcock's film version of John Buchan's thriller 'The 39 Steps'.