The Headwaters Hydrology Project (HHP) is a machine learning (ML)-based streamflow model that provides daily streamflow estimates at the HUC-10 scale across the contiguous United States. Trained on high-quality observed streamflow data (USGS, MT DNRC), hydroclimatic variables, and basin characteristics, HHP delivers seamless, natural streamflow simulations—excluding the effects of dams, diversions, and other human water management influences. A full-page application is available at https://streamflow.climate.umt.edu/.