A vascular flora and annotated checklist are provided for the Salero Ranch, some 6500 hectares of private land in central Santa Cruz County, Arizona. The study area has a history of silver mining and cattle grazing dating back hundreds of years. It is located in the Madrean Sky Islands region near the U.S.–Mexico border and includes parts of the Grosvenor Hills and the foothills of the Santa Rita Mountains. The elevation varies from 1150 to 1934 m, a range of 784 m, and the terrain is rocky, sloped, fractured, and faulted, creating many microhabitats. Scrub or semidesert grassland is the dominant vegetation type; evergreen oak woodland (encinal) is also present. This flora is specimen-based; more than 1640 collections were made between 2013 and 2019 to document 788 species and infraspecific taxa distributed in 445 genera and 103 families. The largest families are Asteraceae (129 taxa at or below the specific level), Poaceae (115), Fabaceae (72), Euphorbiaceae (27), and Malvaceae (27). The largest genera are Muhlenbergia, Euphorbia, Cyperus, Bouteloua, and Dalea. Non-native plants (69) comprise 8.8% of the flora; nearly half (34) of the non-natives are grasses. Significant records include two species new to the United States (Polystemma sp., Apocynaceae; Solanum houstonii, Solanaceae), two species new to Arizona (Ipomoea muricata, Convolvulaceae; Sida glabra, Malvaceae), and new localities for several species with limited distributions in the state. Factors contributing to the floristic diversity are elevational range, topographic complexity, species-rich vegetative communities, and sampling effort. The results of this flora suggest that the grasslands of southeast Arizona—even private ones with a history of intensive use—harbor botanical surprises and high species numbers. NOTE: Species list reflects new finds plus changes and corrections since 2020 publication.