Source: Historical Statistics of the United States 1789-1945In a previous post I speculated about why the Keenans came to the US when they did. I want to update you with some more details and to say that after doing some more research, the picture is still mostly the same.
First, as you've noticed, I have attached a graph showing immigration from Ireland to the US from 1820 through 1880 (In future posts I'll include a graph that goes all the way to 1940). You can see how it starts small during the 1820s and 1830s and then peaks during the famine years of 1850s. I think this puts in perspective even more how the Keenans were very early (1821) compared to the bulk of Irish immigration.
Second, I have been reading parts of Coming to America (Second Edition): A History of Immigration and Ethnicity in American Life by Roger Daniels. It identifies three different periods of Irish immigration: pre-famine, famine, and post-famine. When talking about reasons for immigration pre-famine, the author does indeed say it is a result of overpopulation following the Napoleonic Wars.
This book only talks about it from the perspective of available land and doesn't explicitly talk about food prices, as the Irish history books did. But I think it is still presenting the same picture. Basically, Ireland was becoming overpopulated and in an agricultural society, this means that there isn't enough land available for families to grow enough crops to make a living.
The Napoleonic Wars and the associated increased food prices meant that the reckoning of overpopulation and smaller and smaller plots of land could be postponed - in other words, families could divide up and pass on smaller plots of land but still make money to sustain themselves. But after the war, prices stagnated or declined and so suddenly farmers found their plots weren't enough to survive, or if they were, would not be enough to divide and pass on to their children.
Daniels says that emigration was the only solution to the overpopulation (since industry was nonexistent at the time). And he says that the people that left would have been low income, but not the poorest of the poor. If this is right, the Keenans were poor enough to want to leave, but not so poor that they couldn't afford to leave. So they sought out a new country with land aplenty.
Works Cited:
Coming to America (Second Edition): A History of Immigration and Ethnicity in American Life by Roger Daniels
