What was the Know-Nothings political organization?

The Know-Nothings were members of a secret political group that sprouted in the 1800s amid anti-immigrant sentiment in the United States. They organized to keep foreign-born citizens from holding political office, and to prevent other anti-immigrant and anti-Roman Catholic activities. This was in response to the some 5 million immigrants, many of them Roman Catholics, who arrived in the United States between 1825 and 1855. Know-Nothings went by such names as the Order of the Sons of America in Pennsylvania and the Order of the Star Spangled Banner in New York. They came to be called Know-Nothings because they operated clandestinely and always answered “I don’t know” when questioned about their activities. In 1854, they became the American Party and their candidates won the governor seats in Massachusetts and Delaware.