Heritage language (HL) speakers have received scholarly attention in recent years as an interdisciplinary research theme, but relatively less attention has been paid to their demographics. Existing studies of HL speakers' demographics often focus on young children in areas of high immigrant concentration (i.e., California, Florida, and New York); no study has systematically investigated cross-regional and chronological demographic patterns of adult HL speakers. From the perspective of HLs as a national resource, such demographic data on adult HL speakers are useful to gauge the availability of a bilingual workforce and determine structures needed to support and develop a bilingual U.S. population. Using the "Integrated Public User Microdata Series" (Ruggles & Sobek, 1997), which is based on data from the U.S. Census and the American Community Survey, this study makes geographical and chronological comparisons among groups of adult HL speakers from 1980 to 2010. The data show major differences in the demographics of adult HL speakers in different regions. The analyses also reveal differences by language, specifically between the adult HL speakers of Spanish and other languages. Implications of these patterns are discussed.