[…] Altogether, about a million people in Ireland are reliably estimated to have died of starvation and epidemic disease between 1846 and 1851, and some two million emigrated in a period of a little more than a decade (1845-55). 

[…] in the Irish famine of the late 1840s, successive blasts of potato blight - or to give it its proper name, the fungus Phytophthora infestans - robbed more than one-third of the population of their usual means of subsistence for four or five years in a row.

http://www.bbc.co.uk/history/british/victorians/famine_01.shtml

 

The Illustrated London News, 15th July 1848.

http://www.everyculture.com/multi/Ha-La/Italian-Americans.html

The migration of Jews from Russia to America began in the 1870s, but between 1861 and 1871, only 314 Jews were allowed to emigrate every year. The number increased to 4,304 during the next decade. Then, in April-May 1881, a wave of pogroms* swept through Southern Russian (today, Ukrainian) towns of Yelisavetgrad (today's Kirovograd […] Kiev, […]. The pogroms occurred again, although on a smaller scale, in 1882-1884. Before that, occasional pogroms were only registered in Odessa (1821, 1859, 1871), where they were instigated by the Greeks […]. Panic swept the Jewish population, and it set into motion mass Jewish emigration from Russia to America. 

http://www.rtrfoundation.org/kiev-1.html

*an act of organized cruel behaviour or killing that is done to a large group ofpeople because of their race or religion

The eviction of farmers by Protestant landlords, protected by the police, is a famous topic illustrated by the newspapers at this period.

During the years 1845 – 1849, 500 000 people were evicted.The farms having less than 12.5 acres represented 45% of all the farms in 1841 and only 15% ten years later.

D. Colon (dir.), history book seconde, Belin, July 2010

New York September 22nd 1850 

My D[ea]r Father and Mother, Brothers and Sisters, I write these few lines to you hoping that these few lines may find you all in as good State of health as I am in at present, thank God. […] My D[ea]r father, I must only that this [is] a good place and a good Country for if one place does not suit a Man he can go to another and can very easy please himself. But there is one thing that's Ruining this place especially the Frontier towns and Cities where the Flow of Emmigration is most. The Emmigrants has not money Enough to take them to the Interior of the Country which oblidges them to remain here in [New] York and the like places for which Reason causes the less demand for Labour and also the great Reduction in wages. For this reason I would advise no one to come to America that would not have Some Money after landing here that would enable them to go west in case they would get no work to do here.[...] Come you all together courageously and bid adieu to that lovely place the land of our Birth. […] http://tiara.ie/Margaret_McCarthy_Letter.pdf