Genealogy
As the first British census which aimed to record details about every citizen, the 1841 census is an important genealogical source. However, it has some limitations when compared to later censuses: exact ages are not usually given; relationships between members of the same household are not stated; and people's places of birth are simply noted as within the census county or not (or are quite frequently given as "N.K.", meaning "Not Known").
None of the census records for Ireland prior to 1901 survive, except occasionally in fragments. Some records for the 1841 Census had been transcribed in various places, however, before the original copies were lost or destroyed.
Read more about this topic: United Kingdom Census 1841