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Updated: Oct 31, 2020


Historic maps offer a window to a nation’s past and ultimately to our ancestors’ lives. For researchers interested in Irish Family history, the historic mapping feature found on the Ordnance Survey Ireland (OSI) website provides a vital resource which depicts the transition of the social and historical fabric of Ireland. Many big houses, railway stations and other locations no longer found on modern maps can be located on the nineteenth century maps that are available. Alternatively, modern towns, such as Shannon, did not exist in the 1800s, so the maps enable us to see what existed before the development of these urban settings.



The origins of OSI date from the early 1800s. The story begins with Irish landowners lobbying for a national survey and land valuation. In addition, the taxation system, which was based on townland units was inequitable. Although many maps of Ireland exist for years prior to this period, not all were to scale, boundaries were obscure and elevations were not accurate. A select committee chaired by Thomas Spring Rice, declared that the ‘obscurity and want of uniformity of the general system, as well as the inequality incidental to the mode of apportioning these taxes system’ and necessitated a new map and survey of Ireland.[1] The only other extensive surveys of the county were the Down Survey, conducted in the middle of the seventeenth century by Sir William Petty and the Grand Jury maps in the late eighteenth century.

1655/56: Liberties of the city of Cork

The Spring Rice report provides some detail about the geography of Ireland at the start of the nineteenth century, ‘the Surface of Ireland consists of about 12,000,000 Irish acres or nearly 20,000,000 acres in English measurement, divided into 4 provinces … and a further civil subdivision, already alluded to in this Report, generally known as townlands … the ancient and recognised divisions of the country.[2]

Byzantine mosaic at the Chora Church, Constantinople

Following the Committee report, the Ordnance Survey Office was established in 1824, initially under the auspices of the Army. Due to the ‘general tranquility of Europe’, the army were able to use their considerable and valuable corps of officers to undertake in the precise and engaging work.[3] The entire island of Ireland was surveyed using a scale of 6 inches to 1 mile and was completed in 1846 under the direction of Major General Thomas Frederick Colby. Ireland was the first country in the world to be mapped at such a detailed scale.[4]

Thomas Colby

Figure 3: Thomas Colby

How to use the OSI historic map (Click here to download PDF instruction document)


Further Reading


[1] Report from the Select Committee on the Survey and Valuation of Ireland, HC (1824), 445, viii, 4.

[2] HC (1824), 445, viii, 6.

[3] HC (1824), 445, viii, 10.


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