Shortly before the commencement of the Bank in 1919, Birmingham's boundary had been expanded to include Quinton to the west; Handsworth, Aston, and Erdington to the north; and Kings Norton and Yardley to the south and east. This expansion increased the area of the city from 19.75 square miles to 68.13 square miles, while the population increased from 522,204 (1901 census) to 922,167 (1921 census).
The Bank's initial branch network, established during the first trading period to March 31st 1920, reflected the city's population spread in this period. Most of the twenty branches opened (see first map below) were in the densely populated inner-city area, and these branches attracted the most depositors. Branches opened in the still rural areas such as Erdington, Acocks Green, Kings Heath, and Northfield were opened as part-time Evening Branches, and initially attracted few depositors.
Two years after the Bankís commencement, the County Borough of West Bromwich initiated steps to take over the Urban District Council of Perry Barr. In order to counter this move, both Birmingham and Sutton Coldfield prepared similar claims. Representations were duly made to the Minister of Health, but the time was deemed inopportune. In the meantime, extensive building on the north side of Birmingham as the population of the city left its congested centre for the better living conditions offered on its borders (and the availability of employment in the Witton area), was beginning to overflow the city boundary into Perry Barr.
At this time, Perry Barr had a population of about 3,300. Employment in the area was split almost equally between mining operations for the Hampstead Colliery Company, and agriculture. Perry Barrís income from rates was about £13,700 (compared with Birminghamís £4,072,442), of which a large proportion was absorbed by the costs of the West Bromwich Union workhouse.
The incorporation of Perry Barrís 4,083 acres (6.4-square miles) into Birmingham followed a 1926 referendum in which the ratepayers of Perry Barr voted favourably in the proportion of about twelve to one. The referendum asked the ratepayers to vote in favour of the following resolution:
That this Council considers that the best interests of the Urban District of Perry Barr will be served by its incorporation as soon as possible with the City of Birmingham, and that the Councilís decision is arrived at after full investigation of, among others, the following considerations:
(a) That there is a community of interests between Perry Barr and Birmingham
(b) That Perry Barr should now possess sewerage and sanitary services, the cost of which cannot possibly be met by the rates receivable from Perry Barr.
(c) That in view of the rapid development of Perry Barr which is now taking place, the area should be developed on town planning lines. Perry Barr could not face the expenditure which the preparation of a town planning scheme would involve.
(d) That the rates of Perry Barr and the contributions from the Ministry of Transport do not enable the Council to put and keep its roads in a sufficient state of repair.
That Perry Barr, being an outgrowth of Birmingham, could be more economically and efficiently administered as one unit with Birmingham.
Perry Barr was incorporated into Birmingham from April 1st 1928. Branches of the Bank were soon established at Perry Common, Birchfield, and Kingstanding. In due course, Tower Hill, Perry Beeches and Great Barr branches were also opened within the former urban district.
During the Inter-War years, the city gradually made use of the newly-acquired agricultural land (including the additions of 1931) to develop a number of housing estates. Reference to these individual housing developments is made in the appropriate branch entry on this website. Prior to the outbreak of the Second World War, the Bank had developed a network of 62 branches that administered 466,163 savings accounts.
By 1939, Birmingham's area had grown to 79.89 square miles, and its population was around one million.The city's population has remained around the one million mark since the 1930s, peaking at 1,148,354 at the 1951 census. The last expansion of Birmingham's boundaries brought in Sutton Coldfield to the northeast in 1974, resulting in a total area for the city of 103.39 square miles.
Expansion of the Bank's branch network after the Second World War (see third map below) was less dramatic than in its first twenty years. In 1969, the network peaked at 73 offices as new branches were opened on the outskirts of the city, and inner-city branches were closed either because of lack of demand or demolition as part of redevelopment schemes.
At the time of the BMTSB's cessation in 1979, the population of Birmingham and the adjacent areas in which the Bank had branches was approximately 1.4 million. The number of the Bank's Active Accounts at this same date was approximately 463,000 - a penetration ratio of 33%