In 1870, plans were drawn up to build an extension of the Somerset & Dorset Railway, connecting Evercreech Junction with Bath over the Mendip Hills where a summit would be reached 811 feet above sea level. Its engineers fought a constant battle with the topography - the railway having to create its own level with cuttings, tunnels, embankments and viaducts. Work to built it got underway in 1872, with commercial services first pressing the sleepers on 20th July 1874. Originally built for a single track, the formation and structures as far north as Midford were widened in 1903 as part of a scheme to increase capacity into Bath. This was ultimately abandoned on cost grounds.
The junction between double and single was sited on Midford Viaduct, a structure of eight segmental arches, each 50 feet in span, which carried the line for 168 yards over the B3110, the Somerset Coal Canal (now closed), Cam Brook and the Great Western's Limpley Stoke to Camerton line. The latter passed beneath the third arch from the south - also on a viaduct - and was operational between 1910 and 1951. Track level was 55 feet above the brook, falling to the north on a gradient of 1:60 and curving eastwards on a radius of about 27 chains.
The structure seen today is effectively two viaducts tied together, with the 1903 scheme resulting in it being widened on its west side and seamlessly skinned in engineering brick. Two of the piers are buttressed on this elevation. Below the parapets are masonry string courses; above them are concrete copings topped with posts and handrails.
In 1953, the viaduct featured in the opening sequence of a British film comedy, the Titfield Thunderbolt, about a group of villagers trying to keep their branch line open. Closure came to the S&D 13 years later, with the structure's operational life officially ending on 7th March 1966.
Though generally in fair condition, some of its brickwork is locally spalled and attempts have been made to occasion repairs with patch concrete. Ivy, weeds and saplings are colonising some of the piers and spandrels.
In spring 2005, NCN 24 of the National Cycle Network - known here as the Colliers Way - was routed across Midford Viaduct, avoiding the need to cross the road below. The section through to Wellow is now open, following the former trackbed.