From the sixteenth to the nineteenth century the institution of the landed estate dominated rural Irish society and left an indelible mark on the rural landscape. Landed families carved out demesnes, farms, planned settlements and villages. Estates played a big role in the layout of fields that we see today in Co. Louth and elsewhere around the country.
One excellent online source for exploring these estates in the mid-nineteenth century can be found at the Cross Border Archives Project. The project, which is a joint venture between Newry & Mourne Museum and Louth County Archives Service, uses a linked website to make archives and information on the historical development of the Newry & Mourne – Louth region freely available. Included on the website is a webGIS of Louth Landowners in the 19th century derived from Griffiths Valuation. Griffiths Valuation, also known as the Primary Valuation, was a government survey published between 1847 and 1865 which estimated the value of every farm in the country as a basis for local taxation.
The map was compiled using information in Griffiths Valuation of 1854… ownership of a townland is assigned to a particular landowner if, by the 1854 valuation, they owned more than 75% of the townland.
As well as an interactive map of the principal estates, the website also features information on the background of the landed families.
 Terence Dooley, The big houses and landed estates of Ireland, a research guide, (Dublin, 2007), 80-81.