The island of Ireland is split into 32 different counties, and from 1800 until 1921 the whole island was a part of the United Kingdome of Great Britain and Ireland (although Britain had been a controlling presence on the island for considerably longer than this). In 1921 the island was split into two separate states, where the six counties with the highest population of Protestants formed part of the United Kingdom of Great Britain and Northern Ireland, and the other 26 counties became the Independent Republic of Ireland. From 1821 until 1841, the population of these 26 counties was growing steadily, until the Great Famine from 1845 to 1849 swept across the island, particularly devastating the west and south.

The famine was caused by a Europe-wide potato blight that contributed to mass starvation and death throughout the continent, although it's impact on Ireland was much harsher than anywhere else. The potato blight affected Ireland so severely as the majority of potatoes in Ireland were of a single variety which allowed the disease to spread much faster than in other countries. People in the west and south of Ireland were particularly dependent on potatoes, and these areas were affected more heavily than the north and west, where flax and cereals were the staple. As the potato blight spread, the population became increasingly reliant on dairy and grain products, however a lot of these resources were relocated by the British military to combat food shortages in Britain. Due to disproportional dependency on potatoes, and mismanagement by the British government, over one million people died and a further one million emigrated. The Great Famine lasted from just 1845 to 1849, but it's legacy caused almost a century of population decline, and to this day, the population of Ireland has never exceeded it's pre-famine levels.

The population decline continued well into the twentieth century, during which time the Republic of Ireland achieved independence from the British Empire. After centuries of fighting and rebellion against British rule, Irish nationalists finally gained some independence from Britain in 1921, establishing an Irish Republic in the 26 counties. There was a lot of conflict in Ireland in the early 1900s, through the War of Independence and Irish Civil War, however the population of the Republic began growing again from the 1960s onwards as the quality of life improved and the emigration rate declined. The population was at it's lowest from 1926 to 1971, where it remained at just under three million, but in the following fifty years the population has grown by over two million people.

Abstract copyright UK Data Service and data collection copyright owner.

The purpose of the project was to provide machine-readable economic and social history statistics relating to the whole of Ireland for the period 1821-1971. Further information about the project is available on the QUB Centre for Data Digitisation and Analysis website.


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The dataset contains population census data covering population, housing, religion, birthplaces, language, occupations, age structures, conjugal status and family structure. All the relevant background material is incorporated either in the documentation files or in the scanned images of the tables of contents, prefaces, and notes in the original source. The main population census tables are:

Total population grouped by county districts and gender (1881-1971).

Total number of buildings, classified as either inhabited buildings, uninhabited buildings, or buildings under construction grouped by county districts. Also includes the area and valuation of each county district (1881-1971).

Total number of Roman Catholics, Church of Ireland members, Presbyterians, Methodists and others grouped by county districts and gender (1926-1971).

Total number of Roman Catholics, Church of Ireland members and others grouped by counties, gender and age groups (1926-1971).

Total numbers born in each county grouped by county of residence and gender (1901-1971) Republic of Ireland only.

Total numbers born in each province grouped by county districts of residence and gender (1926-1936) Republic of Ireland only

Total numbers born in each county district grouped by county of residence and gender (1926-1971) Northern Ireland only.

Irish/English speakers and English only speakers grouped by county districts (1926-1971) Republic of Ireland only.

Occupations grouped by counties and gender (1926-1971).

Total number of persons in each age group grouped by county districts and gender (1901-1971).

Total number of married, single and widowed people grouped by county districts, age groups and gender (1926-1971).

Total number of families grouped by duration of marriage, husband's age at marriage, wife's age at marriage and number of children born (1946, 1961 and 1971) Republic of Ireland only.

Total number of families grouped by counties, duration of marriage, wife's age at marriage and number of children born (1946, 1961 and 1971) Republic of Ireland only.

Total number of families grouped by religious affiliation, duration of marriage, wife's age at marriage and number of children born (1946, 1961 and 1971) Republic of Ireland only.

Total number of dependent children grouped by counties, number of children in family and parent's marital status, gender and age (1926 and 1946) Republic of Ireland only.

Please note: this study does not include information on named individuals and would therefore not be useful for personal family history research.

In the past four centuries, the population of the United States has grown from a recorded 350 people around the Jamestown colony of Virginia in 1610, to an estimated 331 million people in 2020. The pre-colonization populations of the indigenous peoples of the Americas have proven difficult for historians to estimate, as their numbers decreased rapidly following the introduction of European diseases (namely smallpox, plague and influenza). Native Americans were also omitted from most censuses conducted before the twentieth century, therefore the actual population of what we now know as the United States would have been much higher than the official census data from before 1800, but it is unclear by how much. Population growth in the colonies throughout the eighteenth century has primarily been attributed to migration from the British Isles and the Transatlantic slave trade; however it is also difficult to assert the ethnic-makeup of the population in these years as accurate migration records were not kept until after the 1820s, at which point the importation of slaves had also been illegalized. Nineteenth century In the year 1800, it is estimated that the population across the present-day United States was around six million people, with the population in the 16 admitted states numbering at 5.3 million. Migration to the United States began to happen on a large scale in the mid-nineteenth century, with the first major waves coming from Ireland, Britain and Germany. In some aspects, this wave of mass migration balanced out the demographic impacts of the American Civil War, which was the deadliest war in U.S. history with approximately 620 thousand fatalities between 1861 and 1865. The civil war also resulted in the emancipation of around four million slaves across the south; many of whose ancestors would take part in the Great Northern Migration in the early 1900s, which saw around six million black Americans migrate away from the south in one of the largest demographic shifts in U.S. history. By the end of the nineteenth century, improvements in transport technology and increasing economic opportunities saw migration to the United States increase further, particularly from southern and Eastern Europe, and in the first decade of the 1900s the number of migrants to the U.S. exceeded one million people in some years. Twentieth and twenty-first century The U.S. population has grown steadily throughout the past 120 years, reaching one hundred million in the 1910s, two hundred million in the 1960s, and three hundred million in 2007. In the past century, the U.S. established itself as a global superpower, with the world's largest economy (by nominal GDP) and most powerful military. Involvement in foreign wars has resulted in over 620,000 further U.S. fatalities since the Civil War, and migration fell drastically during the World Wars and Great Depression; however the population continuously grew in these years as the total fertility rate remained above two births per woman, and life expectancy increased (except during the Spanish Flu pandemic of 1918).

Since the Second World War, Latin America has replaced Europe as the most common point of origin for migrants, with Hispanic populations growing rapidly across the south and border states. Because of this, the proportion of non-Hispanic whites, which has been the most dominant ethnicity in the U.S. since records began, has dropped more rapidly in recent decades. Ethnic minorities also have a much higher birth rate than non-Hispanic whites, further contributing to this decline, and the share of non-Hispanic whites is expected to fall below fifty percent of the U.S. population by the mid-2000s. In 2020, the United States has the third-largest population in the world (after China and India), and the population is expected to reach four hundred million in the 2050s.