The Verdugo Mountains and San Rafael Hills in Los Angeles County, California, are a 21 km (13 mi) long mountainous region that encompasses approximately 14,646 ha (36,192 acres) surrounded by the greater Los Angeles area. Urbanization from the greater Los Angeles area has encroached upon these mountains over the years. Despite the mountains’ proximity to high population densities, recent botanical collections from the range are sparse. The goal of our study was to compile historic and recent botanical collections from the range to document the flora of the Verdugo Mountains and San Rafael Hills. We first compiled information on the natural and cultural history of the study area from literature reviews, internet searches, and local herbaria. We then performed botanical surveys in the Verdugo Mountains and San Rafael Hills to document vascular plant taxa with herbarium vouchers, develop an annotated checklist, describe plant communities, and document fire-following species for the region. The vegetation within the study area was predominantly chaparral (chamise or mixed chaparral) and southern coastal scrub with occasional woodlands (coast live oak or California walnut), riparian communities (California sycamore or mixed riparian woodlands), and grasslands (native bunchgrass or valley and southern coastal grassland). We identified fire-following species from three burn areas in the study area one to five years later. A total of 423 native and 164 non-native taxa were confirmed from the area, including 12 rare taxa.