From 1820 to 1870, millions of immigrants from Ireland and Germany came to the U.S.A. due to extreme hardship at home. These immigrants were not well received by some Americans. Part of the reason for the opposition was religious.
Many were Roman Catholic while most of the U.S. at the time was Protestant. Religious discrimination, combined with the fear of immigrants taking away jobs, led to the formation of the anti-Catholic American Party. They were called the “know-nothings” because they would tell outsiders nothing about their party.
On August 6, 1855, an election day in Louisville, Kentucky, the “know-nothings” formed armed groups to guard the polls. Hundreds were turned away. The situation worsened as an armed mob attacked the new Irish and German citizens and their properties. By the time it was over, more than 100 businesses, private homes, and tenements had been vandalized, looted and/or burned. The riots caused more than ten thousand citizens to pack and leave for good. The loss of population caused dozens of local businesses to close. Empty storefronts and charred ruins lay untouched for years afterward.