The county shrunk in size between 1886 and 1954 when various urban areas on the North Shore and in West Auckland became boroughs and established their own local councils.

[1] Between 1886 and 1954, nine boroughs split from the county as the North Shore and West Auckland began to develop: Devonport in 1886, Birkenhead in 1888, Northcote in 1908, Takapuna in 1913, New Lynn in 1929, Henderson in 1946, Helensville in 1947, Glen Eden in 1953 and East Coast Bays in 1954.

During this period, district offices were set up in many of these centres, including Titirangi, Te Atatū, Huapai, Silverdale and Glenfield.

A 1962 commission recommended replacing the county with a ward-based city in West Auckland, however after six years of appeals, this idea was scrapped.

[7] When the dissolution of the county began to be discussed, a new body was proposed for the western North Shore, formed from the growing centres of Albany and Glenfield, which the ARA predicted would have a greater population than Takapuna City by 1986.