Its national headquarters are in Washington, D.C. Its former executive director, Barry W. Lynn, is an ordained minister in the United Church of Christ,[9] as well as an attorney involved with civil liberties issues.

[10] Officially incorporated on January 29, 1948,[11] the organization aimed to influence political leaders, and began publishing Church & State magazine in 1952 and other materials in support of church-state separation to educate the general public.

[12] Its original founding members were Charles Clayton Morrison, Glenn L. Archer,[2] Edwin McNeill Poteat, G. Bromley Oxnam, and Joseph Martin Dawson.

AU supports the right for gays and lesbians to marry, and opposes laws that would permit government officials, such as county clerks, from invoking religious freedom when refusing to issue such marriage licenses.

[14] Americans United has worked to uphold the federal law that bars non-profit groups, including houses of worship, from intervening in partisan politics.