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The Ordnance Survey (OS) is the government agency responsible for producing mapping for the whole of Great Britain. Maps produced by the OS are at the heart of the Library’s collection of modern printed mapping.

From 1855 to 1894 about 400 towns with populations of over 4000 inhabitants were mapped by the OS at 1:500 scale. These were produced at a time of improvements in town planning and sanitary systems following the Public Health Act, 1848. Plans of many towns were later revised at the expense of the town authorities between 1898 and 1908, some towns conducting their own surveys. These plans provide more detail and textual information than OS 1:2,500 (1st , 2nd and subsequent Edition 25 inch:1 mile maps), often naming buildings such as public houses, stating the uses of commercial and industrial premises, occasionally identifying the functions of individual rooms and even showing details such as lamp posts and man holes.

The 1:500 scale sheets constitute informative plans of urban landscapes at the turn of the 19th / 20th century and can be especially valuable when used in combination with census returns and commercial directories.

The Maps

The Library did not receive mapping under Legal Deposit until 1911 which means that there are gaps in the collection of older OS maps. However, the Library has managed to obtain the bulk of OS material covering Wales, including the plans of 28 Welsh towns, together with the English communities of Birkenhead, Oswestry and Shrewsbury, as well as a large amount of mapping for England and Scotland.

Merthyr Tydfil is the only town in our collection which was mapped at the somewhat smaller scale of 1:528 (120 inches:1 mile). This scale preceded the 1:500 scale and was employed for 29 British towns. Shortly after, this scale was revised to 1:500 to aid metrication.

Graphic indexes were published for all of our Welsh plans and also for most British urban communities mapped at large scale. These indexes comprise small scale maps of each urban area with the 1:500 sheet lines or grid superimposed forming finding aids which show the precise geographical coverage of each 1:500 sheet.

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