The First Amendment's religion clauses, prohibiting Congress from establishing a religion while guaranteeing free exercise, have generated extensive and ongoing constitutional litigation over where the line between permissible accommodation and prohibited establishment falls, addressed through evolving Supreme Court tests including the 1971 Lemon test, later narrowed, and a more recent history-and-tradition approach favored by the Court's current majority, applied in cases spanning school prayer, religious displays on public property, funding for religious schools and, especially since the 2010s, disputes over religious exemptions from anti-discrimination and healthcare mandate laws for businesses and institutions objecting on religious grounds, as in the Supreme Court's 2014 Hobby Lobby and 2018 Masterpiece Cakeshop decisions.
The country's religious landscape has also shaped its politics directly, from the nineteenth-century abolitionist movement's substantial religious motivation to the twentieth-century civil rights movement's roots in Black church leadership under figures including Martin Luther King Jr, and more recently the rise of the religious right as a durable force in American conservative politics from the late 1970s onward, closely tied to evangelical Protestant mobilization around abortion, and, since 2022, the Supreme Court's reversal of the constitutional right to abortion in Dobbs v. Jackson Women's Health Organization.