Grosse-Île was established in the early 1830s to contain immigrants that the Lower Canadian government believed were responsible for causing a cholera epidemic. It was later transferred to the powers of Lower Canada’s higher authority, the Province of Canada. The quarantine housed immigrants plagued with cholera and in 1847, it would primarily house Irish immigrants that were coming to the Province of Canada to escape the Great Famine.
The Great Famine, caused by an infection to the potato named potato blight, forced immigration of over a million people from their home in Ireland to North America. The Irish, too often impoverished and forced into smaller and smaller farms by their Protestant English landowners, sought food for their families by growing potatoes, and it is estimated that 40% of Irish families subsisted on potatoes alone. When the blight hit in 1845 and again in 1846, people died of starvation. In 1847, immigration of those who up to then were able to survive would be common. Great Britain refused to export food to the Irish but instead passed a law to install soup kitchens, a programme that failed less than a year after its beginning. Historians now believe that the Great Famine would cause a population decrease of around 20 to 25%.
Immigration to Canada was cheaper and while some immigrants hoped to stay in Canada, many would want to use Canada as a passing ground to cross to New England to start a new life. Many would travel in lumber ships, by no means equipped for human habitation, and approximately 30% of immigrants would die on the way to North America. Immigrations arriving from Ireland to Canada were quarantined at Grosse-Île, often stationed in the port for days before being allowed to disembark due to attempts to sanitise the boat. Grosse-Île’s doctors would do a cursory check on the health of the new immigrants before being either placed in a hospital on the island to be cured of their illness or on other sites of the island to wait out their quarantine before being given the green light to cross to their final destinations. Those who passed the medical test often found themselves without any accommodations, while those who were in the hospital found no beds to lie in. The personnel working at Grosse-Île, mostly Catholic clergy, would often catch ill and die from the unhealthy conditions and the sickness on the island. A majority of immigrants in Grosse-Île were Irish but would be joined in later decades by German and Scandinavian people.
The quarantine closed in 1937 and is now a national historic site under the control of the federal government. The records that were kept at Grosse-Île are a good way for searching ancestry; a good place to start would be here.