Census returns for England and Wales between 1841 and 1921 are available to view online for free at Hertfordshire libraries.
You can use these websites for free at any Hertfordshire library:
- Find my Past has Hertfordshire's oldest parish registers, the 1939 National Register and the 1921 Census.
- Ancestry holds a selection of Census records.
Both websites also include indexes to births, marriages and deaths.
Census returns for Scotland are available at Scotland's people.
Irish Census returns are available at National Archives of Ireland.