The Know Nothings were a nativist political movement in the United States in the 1850s, officially known as the Native American Party before 1855, and afterwards simply the American Party. Members of the movement were required to say “I know nothing” whenever they were asked about its specifics by outsiders, providing the group with its colloquial name.
Supporters of the Know Nothing movement believed that an alleged “Romanist” conspiracy to subvert civil and religious liberty in the United States was being hatched by Catholics. Therefore, they sought to politically organize native-born Protestants in defense of their traditional religious and political values. The Know Nothing movement is remembered for this theme because Protestants feared that Catholic priests and bishops would control a large bloc of voters.
The Know Nothings supplemented their xenophobic views with populist appeals. At the state level, the party was, in some cases, progressive in its stances on “issues of labor rights and the need for more government spending” and furnished “support for an expansion of the rights of women, the regulation of industry, and support of measures which were designed to improve the status of working people.” It was a forerunner of the temperance movement in the United States.