Corrections to the Census data

The 1901 and 1911 censuses were released between 2007 and 2010. It was the largest digitisation project undertaken by the National Archives until work commenced on the 1926 census.

The project made the 1901 and 1911 census returns and images freely available online for genealogical and research purposes. It successfully provided access to over 8.8 million images and transcribed data from these censuses.

However, there were issues with both the images and the transcribed data. The images were digitised from black and white microfilm, the quality of which does not meet modern archival digitisation standards.

Additionally, gaps in the microfilms resulted in missing townlands and district electoral divisions (DEDs) in the digitised returns. These gaps were then also reflected in the digitised returns that were released online.

Transcription issues also arose, such as blank townland and DED fields, making some returns unsearchable. Unclear text or damaged returns were marked with a “?”, complicating searches. Many Irish language returns were only partially transcribed, particularly in the 1911 census.

The National Archives is now developing a project to have these returns fully transcribed and added to the census website once we have completed the 1926 census. Any further gaps identified will also be included at this stage to make the dataset as complete and as accurate insofar as possible.

Work completed on the 1901 and 1911 censuses

To address these issues, the National Archives has been working for the past 18 months on data cleansing and standardisation. Here are some key improvements:

Digitisation and transcription

Several microfilm reels were digitised, providing 2,667 additional images. The Valentia Island district electoral division was digitised in-house and includes 1,337 rows of census returns across 21 townlands on the island.

In total, 4,416 rows of census returns have been transcribed across 17 counties and 80 townlands.

Data correction process

Over 6,000 rows of census returns were updated to include previously missing townland or DED information, making them searchable on the website. For example, an additional 1,934 rows are now searchable in Westmeath and 800 rows in Wicklow.

Data cleansing

Fields marked with “?” were reviewed and corrected where possible. Around 10,000 fields have been cleansed across the 1901 and 1911 censuses, with a new code system introduced to clarify why a field has not been filled out (e.g., [illegible], [page torn], [text struck through]).

Total corrections to date:

• 1901 : 6,331
• 1911: 23,067

The scale of these two collections is immense, and the improvements made so far are significant. The learning and technology from the 1926 census project will aid future enhancements for the 1901 and 1911 censuses, ensuring better access for all users.

Despite these extensive efforts, some errors may still persist due to the project’s sheer scale and quality of the original microfilm and digitised images. The National Archives remains committed to providing the most reliable and accessible data possible.

New additions

The table below includes information on which counties have had additional census returns transcribed and the number of images that have been added to the website.

• County: Galway
• Transcribe Rows of Data: 1150
• Number of Images: 69
• Townlands: 25
• Name of Townland:
  • Ardrahan North
  • Ballybane
  • Ballyboy
  • Ballyglass West
  • Ballylara
  • Fahys Village
  • Castleboy
  • Curraghmore
  • Carrowkeel
  • Frass
  • Glennaslat
  • Ardagh
  • Balling
  • Curraughmulmurry
  • Keelogues East
  • Keelogues West
  • Kilcolumb
  • Kilmacricard
  • Lisnagieragh
  • Outagh
  • Rosdaul
  • Toberroe East
  • Toberroe West
  • Turlough
  • Tigreenan