The earliest settlement dates back to the late Saxon Period and Wassingtune is specifically named in a charter of 947 AD and during the Norman occupation, the manor of Washington formed part of the large holding of the Lords of Bramber. By the time of the Doomsday Inquest of 1086, the Parish extended to fifty-nine hides, the modern equivalent being about five thousand acres. In the past both the civil and ecclesiastical Parish included a large part of Ashington but the ecclesiastical concerns were separated in 1876 and the civil aspects were divided in 1960. Even though the physical size has thus been reduced, through housing development the actual population has remained fairly constant in recent times. At the time of the last village appraisal which was carried out in the late 1980's, this stood at 1,350 spread over four main areas, the Village proper, Heath Common to the north west and the two housing estates of Montpelier Gardens and Spring Gardens to the north.

Buildings

The oldest part of the village is The Street which has at least two Tudor cottages and a building that was originally a medieval hall house. The Church of St. Mary's is built on an ancient site but the present building dates mostly back to the nineteenth century. The Georgian Vicarage is now a private residence as Washington has become part of a group of Parishes and the official Vicarage is currently situated in the Village of Ashington.

The Village School was opened in 1867 and was enlarged and modernised post World War II. In 1823 a Smock Mill was built on Rock Common but this has subsequently been converted to a private dwelling.

Several of the pre-eighteenth century houses are timber framed with traditional wattle and daub construction. Many of the older buildings are built using local sandstone and flint with mainly clay tiles, the oldest being pegged. Some of the more modern properties have concrete tiles and a small number, including St. Mary's Church are tiled in heavy Horsham stone slabs.

Until the beginning of the 20th Century there were 17 thatched properties but now thatch has mainly disappeared and some houses built during the 19th century were roofed in slate.