Massachusetts Republican Party
The Massachusetts Republican Party was founded in 1854. Drawing together abolitionist and nativist anti-Catholic elements, it quickly became the dominant political force in the state and a powerful arm of the national Republican Party. Significant founding figures include Senator Charles Sumner, formerly of the Free Soil Party, and Speaker of the House Nathaniel Prentiss Banks, formerly of the American Party. 
At the time of the Republican Party's founding in 1854, all of Massachusetts's congressional representatives but Sumner were members of the nativist Know-Nothing Party. However, Banks's role as chairman of the 1856 Republican National Convention, his active support for the Republican presidential nominee John C. Frémont in 1856 and his focus on anti-slavery legislation as Speaker put him at odds with his party. Following the Democratic victory in the 1856 elections and the Dred Scott case in 1857, the national American Party organization collapsed, and most Northern members joined the nascent Republicans. In 1857, Banks ran as a Republican against incumbent Know-Nothing Governor Henry J. Gardner and won a decisive victory.
History of immigration to the United States
Irish and German Catholic immigration was opposed in the 1850s by the Nativist/Know Nothing movement, originating in New York in 1843 as the American Republican Party (not to be confused with the modern Republican Party). It was empowered by popular fears that the country was being overwhelmed by Catholic immigrants, who were often regarded as hostile to American values and controlled by the Pope in Rome. Active mainly from 1854–56, it strove to curb immigration and naturalization, though its efforts met with little success. There were few prominent leaders, and the largely middle-class and Protestant membership fragmented over the issue of slavery, most often joining the Republican Party by the time of the 1860 presidential election.