First Ordnance Survey of Ireland begins

1st January 1825
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The Ordnance Survey of Ireland (1829 - 1842) was the first large-scale survey of an entire country in the world. Acclaimed for their accuracy, these maps are regarded as among the finest ever produced. For the family historian, they can identify the lay of the land in the decades preceding the famine and, most importantly, the homes that had been vacated by the time of Griffith's Primary Valuation.

The Ordnance Survey Office, established in 1824, was created to carry out a military survey of the entire island of Ireland to update land valuations for land taxation purposes. The original survey at a scale of 6 inches to 1 mile was completed under the direction of Major General Colby. Ireland thus became the first country in the world to be entirely mapped at such a detailed scale. When the survey of the whole country was completed in 1846, it was a world first.

Particularly relevant for genealogy or those with an interest in the history of a place, these "6-inch" maps include every tiny house or cabin that was likely occupied before the Famine. The good news is that the OSi has captured this and later mapping data in a digitised format, and they are free to inspect online. 

VIEW MAPS Click here to explore the entire archive of historic maps (for the earliest maps check out the 6-inch colour maps).

READ MORE A short history of the Ordnance Survey on Ireland

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