Matthew Stanley Quay was an American politician of the Republican Party who represented Pennsylvania in the United States Senate from 1887 until 1899 and from 1901 until his death in 1904. Quay's control of the Pennsylvania Republican political machine made him one of the most powerful and influential politicians in the country, and he ruled Pennsylvania politics for almost twenty years. As chair of the Republican National Committee and thus party campaign manager, he helped elect Benjamin Harrison as president in 1888 despite Harrison not winning the popular vote. He was also instrumental in the 1900 election of Theodore Roosevelt as vice president.

The Cameron machine, later known as the Quay machine and Penrose machine, was a Republican political machine in Pennsylvania that controlled much of the state's politics for seven decades. Founded by antislavery Know Nothing and Republican Simon Cameron, it passed into control of his son J. Donald Cameron, later controlled by Matthew Quay and finally Boies Penrose. The organization was financially and fiscally conservative, favoring higher protective tariffs and representing business interests.