The first full government census of Ireland was taken in 1821 with further censuses at ten-yearly intervals from 1831 through to 1911. Sadly, the records of the first four censuses were reduced to ashes in the Four Courts in Dublin during the Civil War. Some information from the 1841 census is still available.
The original census returns for 1861 and 1871 were destroyed shortly after the censuses were taken.
Those for 1881 and 1891 were pulped during the First World War, probably because of the paper shortage. No census was taken in 1921, because of the War of Independence. The first census of the population of the Irish Free State was taken in 1926.
To date censuses have been taken in 1926, 1936, 1946, 1951, 1956, 1961, 1966, 1971, 1979 (the census due in 1976 was cancelled as an economy measure), 1981, 1986, 1991, 1996, 2002 and 2006. The 1926 Census Returns will be released to public inspection in January 2027.
Although the census returns were destroyed for 1821-1891, reports still exist which give us some general data on the population. I have compiled the relevant data for Kilnamona here.
The National Archives have made the 1911 Census available online. They have compiled the 1911 Census of Kilnamona on this page also. I found a few Kilnamona-born people recorded in the 1911 census of England and Wales and have recorded them here.
The release of Ireland's 1926 census returns has been approved by the Irish Government. It is expected to be online by 2016, in time for the anniversary of the 1916 Easter Rising.