Longdendale is a valley mainly in the Derbyshire Peak District in the north west of England, north of Glossop and south east of Holmfirth. The name means "long valley". The River Etherow, a tributary of the River Mersey, rises south of Holmfirth and then flows through a chain of six reservoirs known as the Longdendale Chain: Arnside Reservoir, Bottoms Reservoir, Valehouse Reservoir, Rhodeswood Reservoir, Torside Reservoir, Woodhead Reservoir. There was a seventh reservoir at Hollingworth, but it was abandoned later.
The first railway line between Manchester and Sheffield was constructed between 1839 and 1845 on the south side of the reservoir chain by 1,500 navvies of whom many died and most suffered illness. The three mile long double Woodhead Tunnel was, for a time, the longest tunnel in the country. It was replaced by a single, larger tunnel in 1954. The railway line ceased to be economical, and in 1970, the passenger service ceased, followed in 1981 by the freight service.
The trackbed was taken up, and the Longdendale Trail was constructed. It is now part of the Trans Pennine Trail which, in its turn, is part of the 2000 mile long European walking route E8, from Liverpool to Istanbul.
There are plans afoot to re-open the railway and to re-route the Longdendale Trail parallel to the railway.
The most western part of the Longdendale valley belongs to the metropolitan borough of Tameside, Greater Manchester, comprising Broadbottom, Mottram in Longdendale and Hollingworth.
