The phrase first appears in the United States in 1899 and became common by the 1930s. Fascism tended to be rhetorically linked to Christianity, so using “Judeo-Christian” was an attempt by intellectuals to create a progressive alternative concept. The term not only envisioned Jews as part of a shared tradition with their neighbors but also implicitly included Catholics.

Organizations like the National Conference of Christians and Jews (NCCJ) heavily promoted the concept of religious brotherhood and “Judeo-Christianity.” Starting in 1933 the NCCJ sponsored national speaking tours by three man multi-faith groups made up of a Rabbi, Catholic priest and Protestant minister. These “tolerance trios,” as the media dubbed them, were supposed to combat intolerance and bigotry. In World War II this effort expanded considerably, and the federal government made an effort to have such groups speak in military training camps.

World War II made the idea of “Judeo-Christianity” well known. It was cited as a reason for Americans to fight the Axis. Historian Mark Silk remarks that after revelations about the extent of the Holocaust became public “phrases like ‘our Christian civilization’ seemed ominously exclusive."

With the beginning of the Cold War the idea of Judeo-Christianity became a way for the United States to distinguish itself from the anti-religious Soviet Union. It was an inclusive enough idea that it embraced Protestants, Catholics and Jews, while excluding atheism. By the mid-1950s the term had spread far beyond it's politically progressive roots and had been embraced by conservatives. J.B. Matthews, who worked with Senator Joe McCarthy, for instance declared the Soviets aimed to destroy “Judeo-Christian civilization."

The increasing religious diversity of the United States since 1965, spurred by changes in immigration laws, has made the term less popular among political or religious progressives. Sometimes “Abrahamic tradition” is used instead, which is intended include Muslims. In 2009 President Barack Obama gave a much noted speech where he declared it was incorrect to speak of America as a Christian, Jewish or Muslim nation, because it was a “nation of citizens bound by our ideals and a set of values."

Sources: Kevin M. Schultz. Tri-Faith America: How Catholics and Jews Held America to its Protestant Promise (New York: Oxford University Press, 2010).

Mark Silk. "Notes on the Judeo-Christian Tradition in America." American Quarterly 36, no. 1 (1984): 65-85. doi:10.2307/2712839.