Kensington and Chelsea first originated from Saxon settlements, with both areas mentioned in the Domesday Book of 1086. Royalty first moved into the area in 1689 when William III moved into Kensington Palace. Queen Victoria was born in Kensington Palace in 1819 and continued to reside there until her accession to the throne in 1837. With Queen Victoria’s wishes, the title “Royal Borough” was given to Kensington in 1901, after her death.
In the census of 1801, Kensington was recorded as having a population of 8,500 and Chelsea 11,600. By 1831 this had risen to 20,902 and 32,371 respectively. It was only in 1861 that Kensington overtook its neighbour in population size.
The two boroughs were only united in 1965 to form the Royal Borough of Kensington and Chelsea.
The population of the borough in the most recent census (in 2001) was 158,919
The history of many of the buildings in the area is fascinating. In you are interested in particular streets or small pockets of the borough, I would recommend taking a look at the British History Online website.