In short, the organization's purpose was to "resist the insidious policy of the Church of Rome" and to "place in all offices of honor, trust, or profit... not but native-born Protestant citizens." They were required to keep secret about the group. When asked about it, their response was, "I know nothing."

Not all anti-Catholics belonged to the Know-Nothing party, but they certainly supported it wholeheartedly. In the 1852 elections, the Know-Nothings captured major offices in several American cities. Their high tide came in 1854, when they garnered control of several states on the eastern seaboard. In Massachusetts, they elected seventy-five congressmen, a governor, and all the state officers, and the entire state senate.

By then, historian Ray Allan Billington writes, the Know-Nothings became "the rage of the day." Items with the Know-Nothing label included candy, soap and toothpicks. Stagecoaches and clipper ships were named for it. Members looked forward to the 1856 presidential elections, when they hoped to sweep their candidate into the White House.

Catholics worried over the possibility of an anti-Catholic president. By 1856, however, other issues overshadowed anti-Catholicism. As the country divided over the issues of slavery and national union, and with the rise of a new Republican Party, the Know-Nothing platform took a backseat to the larger questions of the day. As the country advanced toward Civil War, the Know-Nothings faded into the background. With Catholic immigrants shedding their blood in defense of the Union, it seemed ludicrous to question their patriotism.

But the group's demise didn't mean the end of anti-Catholicism, which historian Arthur M. Schlesinger, Sr. calls the longest reigning prejudice in American history. In decades to come, other anti-Catholic groups would gain ground, including the Ku Klu Klan in the 1920's. But none would gain the influence or the numbers that the Know-Nothings had for a brief time in the 1850's.