Environmental mercury (Hg) release and subsequent bioaccumulation is a major concern within protected lands, including US national parks, and it is unclear how changes in Hg emissions and land perturbations will affect Hg concentrations within food webs. No comprehensive conceptual model yet exists of Hg sources, delivery pathways, or Hg evasion mechanisms across the US landscape, despite evidence that Hg concentrations in biota reach levels that can be detrimental to wildlife and human health. Here, we paired Hg stable isotope measurements with the emerging application of dragonflies as biosentinels to examine spatial and temporal patterns of Hg delivery and bioaccumulation across broad geographic regions. Dragonflies were collected across 73 US national parks as part of the Dragonfly Mercury Project and assessed for Hg stable isotopes. Isotopic data were then examined by ecoregion and primary aquatic habitat type (e.g., lentic, lotic, wetland); patterns were compared with geospatial and water quality data to ascertain controls on Hg transport and bioaccumulation. Preliminary results indicate that Hg processes such as photochemical degradation (inferred through Δ199Hg), and atmospheric delivery mechanisms (inferred by Δ200Hg), were recorded in dragonfly tissues. Photochemical-derived fractionation was highly habitat dependent. Hg isotope values in lotic systems were found to be dependent on dissolved organic carbon and geospatial characteristics, whereas lentic systems demonstrated more nuanced trends related to primary productivity and light penetration. Strong patterns for Δ200Hg emerged in the western cordillera region of the US, highlighting the importance of precipitation derived Hg to more arid regions in contrast to mixed sources (gaseous elemental Hg and wet deposition) within wetter, canopy-covered regions of the Pacific Northwest. This work highlights the utility of dragonflies for Hg isotope studies, given their ability to track isotope differences attributed to small-scale habitat changes or larger-scale regional patterns.