Interesting facts from wisconsinhistory.org:
Second only to Germans, close to 4.5 million Irish settled in the U.S. between 1830 and 1920. The main Irish influx in Wisconsin occurred between 1840 and 1860 and they were the largest English-speaking group to settle in the state. Unlike other immigrant groups, the Irish did not move immediately westward after arriving in the U.S.: the average Irish immigrant had spent seven years in the U.S. before moving to Wisconsin. In 1860, the Wisconsin's Irish population numbered 49,961; 41,907 in 1880; and 23, 544 in 1900. Irish immigrants were more likely than other groups to move from county to county and from state to state in search of available land for farming.
more:
Irish in Wisconsin
Links to more:
Early Irish Settlers in Milwaukee
Scotch-Irish Presbyterian Settlers in Southern Wisconsin
The Irish of North Country
Wisconsin Magazine of History : Search Results