Castell-y-Rhingyll is a hamlet that has developed around the cross-roads where the B4297 and the A476 meet, approximately three miles north west of Ammanford. The first edition of the 25inch OS maps shows that in 1889, Castell-y-Rhingyll was a very small settlement surrounded by farms such as Castell-y-Rhingyll; Castell-y-Waun; Pant-y-Meillion and Brynhyfryd. More houses had been built by the second edition, published in 1906. In 1916, the third edition of the 25inch OS maps recorded a Sunday School (NPRN 12713) near the crossroads.
The hamlet expanded considerably during the twentieth and twenty-first centuries. Small housing estates were built along the roads leading to the crossroads, such as Maesymeillion flats - which occupies the south-western part of the crossroads (A476), and The Hollies - which was built along the south-eastern part of the crossroads (B4297). Castell-y-Rhingyll also has a garage and shop, and a large warehouse selling pet care items.
Sources: modern and historic OS maps; google street view
M. Ryder, RCAHMW, 28th November 2018.