Tidmouth is a borough situated on the River Tid Estuary, on Sodor's west coast. With a population of 35,000 in 1951, it is the largest town on Sodor. It is home to the headquarters of the North Western Railway and the main line sheds.
Tidmouth's rise and development is mainly due to the enterprise of A. W. Dry & Co., a drainage company. The harbour, which is deep and well sheltered, has been known for centuries as a safe place in which to ride out storms; but access from land was, until the 1880's, only possible on foot or by pack-pony. The valley of the Tid, north east behind the town, is peculiar in that it is narrow and enclosed by precipitous cliffs; and being throughout on a higher level, the river falls sharply before reaching the sea. Even now there are only footpaths along the valley.
Until well on into the 19th Century it was a rough place, the haunt of smugglers who alternated as fishermen, and who had developed their special kippering process, the secret of which is still jealously preserved today.
A. W. Dry & Co faced considerable opposition when wishing to use the harbour as a base for operations in the Knapford area. Boat building however, was among their various activities, and they had produced a new design of fishing boat which fortunately found favour with the Tidmouth men. This together with judicious "sweeteners" eventually opened the door to an amicable arrangement. Supplies and equipment for the drainage project could then be brought in by sea and conveyed along a coastal road built for the purpose round the headland.
By 1905, the Ulfstead Mining Company had become dissatisfied with Knapford as a port and adopted A. W. Dry's suggestion of extending their tramway along this coastal road to Tidmouth, and Mr. Topham Hatt, a young engineer from Swindon who had lately joined A. W. Dry's staff, built some light steam locomotives for them.
All went well, and trade boomed till an Autumn gale in 1908 destroyed the road and the tramway with it. Trade was disrupted, and numbers of miners were thrown out of work. The situation was desperate. A. W. Dry had a large interest in the mines, and had not yet been paid in full for the drainage work done. With the help of a Treasury Loan they put unemployed miners to work under Mr. Topham Hatt's direction, cutting a railway tunnel through the ridge south of Tidmouth and laying a railway directly from Tidmouth to Knapford. The Tidmouth, Knapford and Elsbridge Light Railway was formed in 1910. Amalgamation with the Wellsworth and Suddery Railway followed in 1912, and brought fresh trade to Tidmouth. But it was only when the double track NWR was completed in 1916, connecting Tidmouth at last with the outside world, that its potential as a harbour was realised, and its development could really begin.
The town's growth as a port and industrial centre has been phenomenal, and it rapidly became the Island's commercial capital. However it still retains many marks of its uncouth origins, and is not attractive to tourists. Nevertheless those ramblers who are bold and dedicated enough to scramble up the steep path beside the Falls of Tid will be rewarded in the valley beyond, which is a place of awesome splendour. Mention of the Falls is a further reminder of Messrs A. W. Dry's enterprise. In 1906, by harnessing the Falls of Tid, Tidmouth became the first town in Sodor to be lit by electricity. Tidmouth received a Royal Charter to become a Borough in 1918.
The North Western Railway moved their main Motive Power Depot and Administrative Headquarters to here from Vicarstown in 1925. The station, known as the "Big Station", has a all-over glass roof spanning four terminal lines and a "through road" leading to Duck's Branch Line. It contains the Fat Controller's main office, and is the station where HM Queen Elizabeth II visited Sodor. The Express departs and returns from here every day.
Though Tidmouth is still in the television series, it has been replaced by Knapford as the biggest station and by Brendam as Sodor's main port. Lower Tidmouth and Tidmouth Hault have also been seen in episodes. The town has appeared regularly since the thirteenth season with the introduction of the Tidmouth Town Square, which appears to have replaced Tidmouth Station. The station is depicted as having two platforms and three through roads, covered by a glass roof.
- Season 2 - Thomas, Percy and the Coal, Bertie's Chase, Percy and the Signal, The Runaway, Better Late Than Never, Break Van, The Deputation, Thomas Comes to Breakfast, Ghost Train, Woolly Bear and Thomas and the Missing Christmas Tree
- Season 3 - Buzz, Buzz, Tender Engines, Escape, Oliver Owns Up and Bulgy
- Season 17 - Gordon Runs Dry (mentioned)
- Season 20 - Blown Away (mentioned)
- Season 21 - Terence Breaks the Ice (mentioned)
- During Clive Spong's time as illustrator, the station was usually incorrectly depicted as having six terminal roads, with the "through" road outside the station's glass roof.
- The town's motto is "Industry and Progress". Tidmouth's Coat of Arms features a smith's hammer and tongs, a lymphad, three herrings and a wheel. These cover all of Tidmouth's titles to importance: shipping, transport, fishing and engineering. The coat of arms was suggested by George Awdry.