Grass Mountain, in Bennington County in southwestern Vermont, stands between Big Spruce Mountain to the north and Spruce Mountain to the southeast within the Hudson River watershed. Water from its north side flows to the Batten Kill, and its east side drains through Dry Brook into the same river system. To the south, runoff reaches Little White Creek, then the Walloomsac and Hoosic rivers before entering the Hudson. The mountain’s west side drains by way of White Creek and Owl Kill to the Hoosic, showing how the mountain feeds several tributaries within the broader Hudson basin.