Snowmelt-driven floods result in large societal and economic impacts on local communities including infrastructure failures in the U.S. However, the current U.S. government standard design precipitation maps are based on liquid precipitation data (e.g. National Oceanic and Atmospheric Administration’s Precipitation-Frequency Atlas 14; NOAA Atlas 14) with very limited guidance on snowmelt-driven floods. In this study, we developed 25- and 100-year return level design snow water equivalent (SWE) and snowmelt maps using long-term observation-based gridded SWE incorporating the national snow model product (SNOw Data Assimilation System; SNODAS) over the contiguous U.S. The magnitudes of design snowmelt from this study exceed the NOAA Atlas 14 design precipitation maps by up to 140 and 200 mm in the northeastern U.S.; 160 and 240 mm in the north central U.S.; and 190 and 300 mm the western mountain U.S. for the 25- and 100-year return levels, respectively. The snowmelt frequency estimates from this study complement the NOAA Atlas 14 design precipitation and may provide additional guidance on infrastructure design for snowmelt- flooding over snow-dominant regions in the continental U.S.