In mid 1800s, Rhyl was one of the first towns in North Wales to get a gas supply. At first it was owned by a small private company engaged in providing mainly street lighting. Eventually businesses and private households were connected, although poorer townspeople were not able to afford it.
In mid 1890s the newly formed Rhyl Urban District Council bought the gas supply and the water supply. (In due course the council would operate the electricity supply as well - and manage the schools and hospitals. It was a far more powerful body than the present town council.)
The Gas Works were rebuilt /modernised/enlarged in 1929-30 and again in 1943-44 by which time Rhyl was supplying gas to Rhuddlan, Kinmel Bay and Abergele.
The following has been amended in accordance with information received from George Owen:
The big photo at the top shows demolition of a large building on the gas works site in 1962; this was replaced by a smaller building. The other pictures are probably from later in 1960s, by which time the technology involving the big round gasometers had been made redundant by the availability of natural gas.
SAT 7th NOV 2015 UPDATE: Found this on Internet described as c.1920: