The last US government survey that collected information on religious identification was in 1957. Since then researchers have relied solely on non-governmental data sources, primarily the General Social Survey. This paper shows how the American Religious Identification Survey (ARIS) series has deepened understanding of religious identification in the past two decades with its large samples (113 713 in 1990, 50 280 in 2001, and 54 461 in 2008) and its unique open-ended religion question. Giving respondents a chance to name their own religion, if any, allows researchers to identify and study small religious groups, which are placed together under ‘other’ in typical national studies. By using a consistent research methodology, the ARIS surveys form a time-series that enable tracking trends. The paper describes two case studies: how the ARIS series documented the rise of the Nones and how it tracked shifts in religious identification among American Latinos.