From 1845 up until 1850, the Great Irish Potato Famine claimed roughly a million lives due to potato rotting and lack of potatoes. However, not only did roughly one million people die, but approximately double that amount fled the country.

The clear majority emigrated to the United States of America, whereas many also migrated to Canada, the United Kingdom (Great Britain), Australia and others.

Today, roughly 36 million Irishmen and Irish women live in the US. Approximately 14 million live in the UK, seven million in Australia and just over five million in Ireland.

More Info: en.wikipedia.org