Chelsea London is an 1881 census registration district in the county of London
Registration districts were originally created for the registration of births, marriages and deaths, rather than specifically for the census. In many cases, registration districts were broadly equivalent to parishes, but not necessarily so.
https://britishsurnames.co.uk/1881census/london/chelsea-london
https://britishsurnames.co.uk/1881census/london/chelsea-london