The Llanidloes and Newtown was the first railway in central Wales. It opened on 4th August 1853 [i]. 

The source reported that "A large circle was formed in the field adjoining the Station, and Mr. Whalley intro-duced to those assembled Mrs. Owen, of Glansevern, who declared the line to be opened." It hardly required her stirring words to enlist the enthusiasm of the company concerning the economic change which the rail-ways were to bring to Wales. Derelict acres were to be brought into cultivation; "the very central town of the ancient Principality," in which that ceremony was taking place, was to become the capital of a new prosperity, and as for Mr. Whalley, were not that day's proceedings"... "a chapter more honourable than any wreath of laurel that could be won on the battle field by success in war?" The plaudits of the assembled confirmed the senti-ment" [ii]

Reference:
[i] http://spellerweb.net/rhindex/UKRH/GreatWestern/Narrowgauge/Llanidloes.html
[ii] Gasguoine, C. P. The Story of the Cambrian: A Biography of a Railway.: (Wrexham and Oswestry, Woodall, Minshall, Thomas & Co, 1922) pp. 23-24