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Maps: Ordnance Survey maps

The OS County Series, ca. 1850-1940

The enormously detailed OS County Series maps made by the Ordnance Survey are our most popular collection. Most of the British Isles has been mapped at scales of 1:2,500 (25 inches to one mile) since the mid-nineteenth century. Individual roads, buildings and field boundaries can be easily identified. They are held as paper maps, and can be ordered by Map Room staff to the RBMSS reading room in the Weston Library.


The sheet referencing system is rather complicated. From the 1860s until the 1940s, mapping at this scale was done by county. Maps are identified by county and sheet number, and each sheet is divided into 16 sub-sheets. To find which maps cover your area of interest, see the box on the right, or contact Map Room staff for help.


This series covers the following:

  • All of the counties in the British Isles were mapped in their entirety in the nineteenth century (1st edition) and then again in the very late nineteenth or early twentieth century (2nd edition).
  • Most of the maps were updated once or twice more after this between 1900 and the 1940s (3rd and revised editions).
  • Updates were done piecemeal depending on how much change each individual map needed.
  • A few weren’t updated again at all until a new mapping system was introduced after the Second World War. 
  •  After this a new system was introduced, the National Grid (see box below).
  •  General large scale mapping was done at two scales:

 6” to the mile (1:10,560)  - i.e. 6 inches on the map represent one mile on the ground.
25” to the mile (1:2,500) – i.e. 25 inches on the map represent one mile on the ground.

  • Coverage at 6” to the mile is complete for the whole British Isles. A few mountain and moorland areas (such as Dartmoor) are not fully covered at 25” to the mile.
  • Large scale OS mapping can only be ordered by staff. The Map Room holds indexes that can be used to locate the correct sheet number on the old County Series sheetlines, if you contact us with details of the location that interests you or its National Grid reference.
  • Smaller scale OS map series are less complicated and can be ordered like any other series mapping.


Large scale National Grid maps, 1950s to present day

Large scale OS maps have been produced on the National Grid system since the 1950s.

  • Maps dating from the 1950s to the 1990s can be ordered using the National Grid reference.
  • Staff have to order these for you as they can't be ordered on SOLO.
  • More recent large scale OS mapping (between the late 1990s and the present day) is available in digital format but can only be seen in the RBMSS reading room in the Weston Library.
  • Current OS digital mapping data is also available freely from the Ordnance Survey via OS OpenData.
  • A full guide to the National Grid system is produced by the OS and can be used to find the grid reference to your site of interest - see link below.

Finding the maps you need

The easiest way to find out which OS large scale sheets cover your area, is to use the online index produced by the National Library of Scotland. This covers the whole of Great Britain and can be found here. Search by place name and map scale, and it will list all the published sheets that cover that place, with an index diagram to show sheet coverage.

We also have paper indexes in the Map Room which you can consult when visiting.

EDINA Digimap

If you are a current member of the University of Oxford, or of another HEI that subscribes to the EDINA Digimap service, then you can use the service to view a selected range of historical and modern large scale OS maps for Great Britain, dating from the 1840s to the present day.

Digimap can also be used to download data to create your own maps.