It opened in 1867 but from 1868 until closure in 1966 it was operated by the Midland Railway. A brief history of the line by Michael Hoy is available in the Gloucestershire Society for Industrial Archaeology (GSIA) Journal for 1987 pp 2-16.
The Stonehouse and Nailsworth Railway, in Gloucestershire, UK, was a branch line linking the town of Nailsworth to the Gloucester to Bristol mainline at Stonehouse, a distance of 5¾ miles. It also had a short branch line of 1¼ miles from Dudbridge to Stroud.
The Rev W V Awdry (1911 – 1997) who created Thomas the Tank Engine was a member of GSIA almost from its formation in 1964 and its President from 1982 to 1997.
About the time of the closure in 1966 he made a detailed photographic record of the line which includes the stations and associated buildings, the bridges, notices, signals and the permanent way of which more than 130 images are available here.
An appreciation of the life of the Rev Awdry appeared in the GSIA Journal for 1987 page 2.
The route may be seen on the OS map at 1:2500 (25 miles to the inch) of 1902 on the National Library of Scotland Map Images website. Stonehouse Dudbridge Stroud Nailsworth