| 1801 | 1,486 | 1891 | 40,917 | |
| 1811 | 2,782 | 1901 | 43,265 | |
| 1821 | 2,062 | 1911 | 50,830 | |
| 1831 | 3,961 | 1921 | 55,007 | |
| 1841 | 6,471 | 1931 | 48,746 | |
| 1851 | 14,999 | 1941 | 43,740 | |
| 1861 | 32,299 | 1951 | 40,932 | |
| 1871 | 37,774 | 1961 | 39,155 | |
| 1881 | 35,514 | 1971 | 37,775 |
| Richard Fothergill & Henry Richard: | 1868–1874 | |
| Henry Richard & Charles Herbert James: | 1874–1888 | |
| David Alfred Thomas & William Pritchard Morgan: | 1888–1900 | |
| David Alfred Thomas & James Keir Hardie: | 1900–1910 | |
| James Keir Hardie & Edgar Rees Jones: | 1910–1915 | |
| Edgar Rees Jones & Charles Butt Stanton: | 1915–1918 |
| Charles Butt Stanton: | 1918–1922 | |
| George Henry Hall: | 1922–1946 | |
| David Emlyn Thomas: | 1946–1954 | |
| Arthur Reginald Probert: | 1954–1974 | |
| Ioan Lyonel Evans: | 1974–1984 | |
| Ann Clwyd | 1984–2019 | |
| Beth Winter | 2019 to date |
Cynon Valley History Society is a Registered Charity. Charity No. 510143.
All information © Cynon Valley History Society