The hospital was planned in the late 19th century to accommodate sufferers of smallpox, which had reached epidemic levels in London.

[1] It replaced three hospital ships based nearby in Long Reach, Gravesend 15 miles downriver from London Bridge on the Thames.

[2][Note 1] The ships, Atlas, Endymion and the Castalia, were made fast in 1883 at their new custom built moorings, they were in-line, connected by bridges 150 yards from the riverbank.

[4] Designed by the Metropolitan Asylums Board architects A & C Harston,[4] the hospital was built on the former Joyce Green estate, whose area totalled 218 acres (88 ha).

[5] [1] The building of the hospital was delayed due to disagreements with the Local Government Board over the proposed size.

The main hospital housing diphtheria and scarlet fever cases, and later also catering for measles and whooping cough patients too.

[9] During World War I, The Orchard was used as a military hospital, mainly catering for Australian troops.

[4] The Long Reach was maintained in a condition of instant readiness, with a skeleton staff at all times.

[6] In the 1950s, the hospital became used as a training ground for fever nurses, due to the existing facilities for treating infectious diseases.

[10] The Long Reach site treated its final patients in 1973, and the buildings were demolished two years later to facilitate the construction of a new flood barrier.