1885–1918

• The Sessional Divisions of Dengie, Orsett, and Rochford; and
• The civil parishes of Rainham and Wennington.^[1]

Formed primarily from the abolished South Division of Essex, together with the southern part of the abolished East Division (Dengie peninsular). See below for areas covered.

1918–1945

• The Urban Districts of Grays Thurrock, Shoeburyness, and Tilbury;
• The Rural Districts of Orsett and Rochford; and
• Part of the Rural District of Billericay.^[2]

Gained southernmost parts of Chelmsford Division of Essex, including Billericay. The area between River Crouch and River Blackwater (Dengie peninsular), including Burnham-on-Crouch, was transferred to Maldon and the westernmost area, including Rainham, to Romford. Parts comprising Southend-on-Sea County Borough created as a separate Parliamentary Borough.

1945–1950

• The Urban Districts of Benfleet, Billericay, Canvey Island, and Rayleigh;

• The Rural District of Rochford; and

• Part of the County Borough of Southend-on-Sea.^[2]

The House of Commons (Redistribution of Seats) Act 1944 set up Boundaries Commissions to carry out periodic reviews of the distribution of parliamentary constituencies. It also authorised an initial review to subdivide abnormally large constituencies in time for the 1945 election.^[3] This was implemented by the Redistribution of Seats Order 1945 under which South East Essex was divided into two constituencies. As a consequence, the Urban District of Thurrock (created largely from amalgamating the Urban Districts of Grays Thurrock and Tilbury and the Rural District of Orsett) was formed as the new Thurrock Division of Essex.  Other marginal changes resulting from changes to local authority boundaries.

Following the First Periodic Review of Westminster constituencies the seat was abolished. The bulk of the Division, comprising the Urban Districts of Benfleet, Billericay, Canvey Island and Rayleigh, formed the new County Constituency of Billericay. The Rural District of Rochford, and the parts of the County Borough of Southend-on-Sea (Shoeburyness), included in the new constituency of Southend East.

1955–1974

• The Urban Districts of Benfleet, Canvey Island, and Rayleigh; and
• The Rural District of Rochford.^[2]

Re-established as a County Constituency. Benfleet, Canvey Island and Rayleigh were transferred back from Billericay, and Rochford from Southend East.

1974–1983

• The Urban Districts of Benfleet, Canvey Island, and Rayleigh.

The Rural District of Rochford was now transferred to Maldon.

On abolition for the second time, Benfleet and Canvey Island (which now comprised the District of Castle Point) formed the new constituency of Castle Point. Rayleigh had been incorporated into the District of Rochford and was included in the new constituency of Rochford.

Areas covered

MPs 1885–1950

MPs 1955–1983

Elections in the 1880s

Elections in the 1890s

Elections in the 1900s

Elections in the 1910s

General Election 1914–15:

Another General Election was required to take place before the end of 1915. The political parties had been making preparations for an election to take place and by July 1914, the following candidates had been selected;

• Unionist: Rupert Guinness
• Liberal:

Elections in the 1920s

Elections in the 1930s

Elections in the 1940s

Elections in the 1950s

Elections in the 1960s

Elections in the 1970s