<P> Native tolerance, however, was also a very important factor in Irish integration (into Southern society)... Upper - class southerners, therefore, did not object to the Irish, because Irish immigration never threatened to overwhelm their cities or states...The Irish were willing to take on potentially high - mortality occupations, thereby sparing valuable slave property . Some employers objected not only to the cost of Irish labor but also to the rowdiness of their foreign - born employees . Nevertheless, they recognized the importance of the Irish worker to the protection of slavery...The Catholicism practiced by Irish immigrants was of little concern to Southern natives . </P> <Table> <Tr> <Th_colspan="4"> Irish immigration to the United States (1820--2004) </Th> </Tr> <Tr> <Td> Period </Td> <Td> Number of immigrants </Td> <Td> Period </Td> <Td> Number of immigrants </Td> </Tr> <Tr> <Td> 1820--1830 </Td> <Td> 54,338 </Td> <Td> 1911--1920 </Td> <Td> 146,181 </Td> </Tr> <Tr> <Td> 1831--1840 </Td> <Td> 207,381 </Td> <Td> 1921--1930 </Td> <Td> 211,234 </Td> </Tr> <Tr> <Td> 1841--1850 </Td> <Td> 780,719 </Td> <Td> 1931--1940 </Td> <Td> 10,973 </Td> </Tr> <Tr> <Td> 1851--1860 </Td> <Td> 914,119 </Td> <Td> 1941--1950 </Td> <Td> 19,789 </Td> </Tr> <Tr> <Td> 1861--1870 </Td> <Td> 435,778 </Td> <Td> 1951--1960 </Td> <Td> 48,362 </Td> </Tr> <Tr> <Td> 1871--1880 </Td> <Td> 436,871 </Td> <Td> 1961--1970 </Td> <Td> 32,996 </Td> </Tr> <Tr> <Td> 1881--1890 </Td> <Td> 655,482 </Td> <Td> 1971--1980 </Td> <Td> 11,940 </Td> </Tr> <Tr> <Td> 1891--1900 </Td> <Td> 388,416 </Td> <Td> 1981--1990 </Td> <Td> 31,969 </Td> </Tr> <Tr> <Td> 1901--1910 </Td> <Td> 399,065 </Td> <Td> 1991--2004 </Td> <Td> 62,447 </Td> </Tr> <Tr> <Th_colspan="4"> Total: 4,787,580 </Th> </Tr> <Tr> <Td> </Td> </Tr> </Table> <Tr> <Th_colspan="4"> Irish immigration to the United States (1820--2004) </Th> </Tr> <Tr> <Td> Period </Td> <Td> Number of immigrants </Td> <Td> Period </Td> <Td> Number of immigrants </Td> </Tr>

When did the first irish immigrants come to america