Strontium isotope ratios of hair may be a valuable tool to estimate human provenance. However, the systematics and mechanisms controlling spatial variation in Sr-87Sr-86 of modern human hair remain unclear. Here, the authors measure Sr-87Sr-86 of hair specimens from across the USA to assess the presence of geospatial relationships. Ninety-eight human hair specimens were collected from salon/barbershop floors in 48 municipalities throughout the conterminous USA. Sr and Sr-87Sr-86 ratios were measured from hair using quadrupole and multi-collector inductively coupled plasma mass spectrometers, respectively. The Sr and Sr-87Sr-86 ratios of hair were compared with the measured Sr and Sr-87Sr-86 ratios of tap waters from the collection locations. In addition, the Sr-87Sr-86 ratio of hair was compared with the modeled ratios of bedrock and surface waters. Hair color was independent of the Sr-87Sr-86 ratio, but related to Sr. The Sr-87Sr-86 ratios of hair and leachate were not statistically different and were positively correlated; however, in several hair-leachate pairs, the ratios were conspicuously different. The Sr-87Sr-86 ratios of both hair and leachate were linearly correlated with tap water. The Sr-87Sr-86 ratio of hair was also significantly correlated with the modeled ratio of bedrock and surface waters, although the Sr-87Sr-86 ratio of hair was most strongly correlated with the measured ratio of tap water. The Sr-87Sr-86 ratio of hair is related to the ratio of tap water, which varied geographically. The ratio of hair provided geographic information about an individual's recent residence. Differences in the Sr-87Sr-86 ratios of hair and hair leachate may be concomitant with travel and could potentially be used as a screening tool to identify recent movements.