1840 Population Act
By the 1840s the Industrial Revolution had changed the socio-economic and cultural structure of the nation forever. The population had nearly doubled since the original census of 1801 and the census had to move with the changing times. The 1821 census had been a major influence on the 1832 Great Reform Act, but the 1841 census is considered the first modern census and forms the basis of the method still used today. Each person had to give their name, age, sex, occupation, whether born in the county and the country of birth if not England or Wales. These details are why this census is seen as the first census of real value to family historians. This document, the Population Act 1840, provided the legal framework for these changes and created the post of Registrar General of England and Wales whose first occupant was John Lister.
An Act for taking an Account of the Population of Great Britain
Parliamentary Archives, HL/PO/PU/1/1840/3&4V1n273