Longevity, as a complex life-history trait, shares an ontogenetic relationship with other quantitative traits, such as epigenetic and environmental factors. Therefore, it is important to identify environmental factors that may modify the epigenome to establish healthy aging. This study explored the association between tap drinking water and longevity in Cilento, Italy, to understand whether trace elements in local drinking water may have an influence on old, nonagenarian, and centenarian people and promote their health and longevity. Data on population and water sources were collected through the National Demographic Statistics, the Cilento Municipal Archives, and the Cilento Integrated Water Service. Ordinary least squares (OLS) regression and a geographically weight regression (GWR) model were used to study the spatial relationship between the explanatory and outcome variables of longevity. The results of the study showed that the prevalence of longevity is concentrated in the central, northern and southeastern areas of the territory and that some trace elements present in tap water may contribute to local longevity in Cilento. Specifically, all Cilento municipalities had alkaline tap water, and the municipalities with the highest longevity concentrations had higher alkalinity levels than the other municipalities, soft to medium-hard water hardness, an amount of total dissolved solids equivalent to the level of excellent water, lower amounts of sodium, adequate iron concentration, and adequate dietary intake of manganese per day.