In a map of Chelsea made in 1664 by James Hamilton, the course of the original rivulet is clearly shown. The northern boundary of Chelsea begins at Knightsbridge. The north-western, that between Chelsea and Kensington, runs down Basil and Walton Streets, and turns into the Fulham Road at its junction with the Marlborough Road. It follows the course of the Fulham Road to Stamford Bridge, near Chelsea Station. The western boundary, as well as the eastern, had its origin in a stream which rose to the north-west of Notting Hill. Its site is now occupied by the railway-line (West London extension); the boundary runs on the western side of this until it joins an arm of Chelsea Creek, from which point the Creek forms the dividing line to the river.
The parish of Chelsea, thus defined, is roughly triangular in shape, and is divided by the King's Road into two nearly equal triangles.
An outlying piece of land at Kensal Town belonged to Chelsea parish, but is not included in the borough.
The population in 1801 was 12,079. In the year 1902 (the latest return) it is reckoned at 73,842.
Bowack, in an account of Chelsea in 1705, estimates the inhabited houses at 300; they are now computed at 8,641.
The first recorded instance of the mention of Chelsea is about 785, when Pope Adrian sent legates to England for the purpose of reforming the religion, and they held a synod at Cealchythe.
In the reign of Edward the Confessor Thurstan gave Chilchelle or Chilcheya, which he held of the King, to Westminster Abbey. This gift was confirmed by a charter which is in the Saxon language, and is still preserved in the British Museum. Gervace, Abbot of Westminster, natural son of King Stephen, aliened the Manor of Chelchithe; he bestowed it upon his mother, Dameta, to be held by her in fee, paying annually to the church at Westminster the sum of £4. In Edward III.'s reign one Robert de Heyle leased the Manor of Chelsith to the Abbot and Convent of Westminster during his own lifetime, for which they were to make certain payments: "£20 per annum, to provide him daily with two white loaves, two flagons of convent ale, and once a year a robe of Esquier's silk." The manor at that time was valued at £25 16s. 6d. The Dean and Chapter of Westminster hold among their records several court rolls of the Manor of Chelsea during the reigns of Edward III. and Richard II. With the exception that one Simon Bayle seems to have been lessee of the Manor House in 1455, we know nothing definite of it until the reign of Henry VII., after which the records are tolerably clear. It was then held by Sir Reginald Bray, and from him it descended to his niece Margaret, who married Lord Sandys. Lord Sandys gave or sold it to Henry VIII., and it formed part of the jointure of Queen Catherine Parr, who resided there for some time with her fourth husband, Lord Seymour.