American Party is the name of several political in United States history. The first established American party—also called the Know-Nothing party was founded in New York City in 1849 as a secret patriotic organization under the name of the Order of the Star Spangled Banner.

Know-Nothing Movement, a nativist political movement in the United States in the 1850's. It was organized to oppose the great wave of immigrants who entered the United States after 1846. Know-Nothings claimed that the immigrants—who were principally Irish and Roman Catholic threatened to destroy the American experiment. The Roman Catholic church, they charged, was subservient to a foreign prince (the pope), it was growing in power, and it potentially could exert political control over a large group of people. Such nativist sentiments had long existed among many Americans, but they had never before been expressed in such powerful form.

In several Northern states as early as the 1840's there were local nativist parties that drew support from the Democratic and Whig parties. By the early 1850's there was a trend to organize nationally against the presumed immigrant threat. The old parties, the nativists said, had not confronted the danger. The Democrats, it was charged, were supported by the aliens; the party needed their votes and catered to their whims. The Whigs appeared helpless before them.

Originally, nativist party members had worked through a number of secret societies, clandestinely throwing their support on election day with powerful effect to sympathetic candidates. Saying that they knew nothing about such activities, the nativists wreaked havoc with their votes in 1854 in the existing party system. They won sweeping victories at the state and congressional levels. They attracted many Northern Whigs to their point of view along with an important number of Democrats. Southern Whigs also joined because of growing sectional tensions caused by the reintroduction of the slavery issue into national politics in 1854. For a time it seemed as if the Know-Nothings would be the main opposition party in the United States. Publicly backing Millard Fillmore as a presidential candidate in 1856, they won more than 21% of the popular vote and eight electoral votes.

Their platform was inspired by the fear and resentment of native Protestants at the flood of the Roman Catholic immigrants from Europe, and chiefly Ireland, who, on obtaining naturalization, voted themselves into political office in large cities. Their state and national platforms demanded that immigration be limited, that politics be "purified" by limiting officeholding to native-born Americans, and that a 21-year wait be imposed before an immigrant could become a citizen and vote. They also sought to limit the sale of liquor, to restrict public-school teaching to Protestants, and to have the Protestant version of the Bible read daily in classrooms.

Despite their strength and appeal, the Know-Nothings were already in decline as a national party by 1856. Beset by differences over the slavery issue, many members joined the Republican Party, which seemed sympathetic to much of their nativism and offered additional appeals on other important issues. Know-Nothing parties remained strong in a number of Northern states in the late 1850's, but the party was spent as a national force before the election of 1860.

Essentially, the party’s tenets were those of the American Republican Party founded a few years earlier which had subsequently changed its name to the Native American Party. Among other parties so named was one organized in Philadelphia in 1887. At the convention held in Washington, D.C., on August 14, 1888 it nominated presidential candidates. The party platform advocated 14-year residence for naturalization, exclusion of socialists, anarchists and other supposedly dangerous persons, free schools, a strong navy and coastal defense, continued separation of church and state, and enforcement of the Monroe doctrine. Its candidate, James L. Curtis of New York, recieved only 1,591 votes at the November election. In the 1924 elections a similarly named party sought Ku Klux Klan support for its candidates, Gilbert O. Nations for president and C.H. Randall for vice president, nominated at Columbus, Ohio on June 3. This party also gained a negligible fraction of the vote.