The Rural District of Rochford and the former Urban District of Shoeburyness (which had been absorbed by the County Borough of Southend-on-Sea) had previously been part of the abolished South-Eastern Division of Essex.
This passage describes a historical administrative division change in Essex, England. The Rural District of Rochford and the former Urban District of Shoeburyness were once part of the South-Eastern Division of Essex but have since been absorbed into the County Borough of Southend-on-Sea.