The Lower San Francisco study area consists of about 40 sq mi, in a strip between 1 and 6 mi wide, along a 20-30 mi stretch of the San Francisco River in Arizona and New Mexico. The study area and contiguous roadless areas were examined for mineral potential and found to have an area of probable mineral-resource potential for base- or precious-metal deposits in middle to upper Tertiary volcanic rocks. The entire area has a largely unassessable potential for base-metal deposits related to igneous intrusives of Laramide age, like those in the nearby Morenci mining district, Arizona. The contiguous roadless area has an area of probable mineral-resource potential for molybdenum or copper deposits related to intrusive igneous rocks in the core of a dacitic volcano of Oligocene age. An area in the west part of the study area has a probable geothermal-resource potential.