There was an additional category of large burgh in the Scottish system (similar to a municipal borough in England and Wales), which were responsible for all services apart from police, education and fire.

County boroughs to be constituted in this era were a mixed bag, including some towns that would continue to expand such as Bournemouth and Southend-on-Sea.

Upon recommendation of a commission chaired by the Earl of Onslow, the population threshold was raised to 75,000 in 1926, by the Local Government (County Boroughs and Adjustments) Act 1926, which also made it much harder to expand boundaries.

Due to a decline in the heavy industries of the town, by 1932 more than half the male population was unemployed, resulting in very high municipal rates in order to make public assistance payments.

[4] A royal commission was appointed in May 1935 to "investigate whether the existing status of Merthyr Tydfil as a county borough should be continued, and if not, what other arrangements should be made".

[5] The commission reported the following November, and recommended that Merthyr should revert to the status of a non-county borough, and that public assistance should be taken over by central government.

In the event county borough status was retained by the town, with the chairman of the Welsh Board of Health appointed as administrative adviser in 1936.

[6] After the Second World War the creation of new county boroughs in England and Wales was effectively suspended, pending a local government review.

[7] The Local Government Boundary Commission was appointed on 26 October 1945, under the chairmanship of Sir Malcolm Trustram Eve,[8] delivering its report in 1947.

The recommendations of the commission extended to a review of the division of functions between different tiers of local government, and thus fell outside its terms of reference, and its report was not acted upon.

In England, most of those former county boroughs that did not gain unitary authority status—Barrow-in-Furness, Burnley, Canterbury, Carlisle, Chester, Eastbourne, Gloucester, Great Yarmouth, Hastings, Ipswich, Lincoln, Northampton, Norwich, Oxford, Preston, and Worcester—have given their names to non-unitary local government districts (in some cases coterminous with the old county borough, in other cases much larger).

Although unitary authorities are functionally equivalent to county boroughs, only in Wales is the title given official recognition by Act of Parliament.

This table shows those county boroughs that existed in England and Wales between the Local Government Acts of 1888 (that created them) and 1972 (that abolished them from 1974).

In the Republic of Ireland, the relevant legislation remained in force (although amended), and county boroughs on the original model existed until 2001.