When The Jepson Manual: Higher plants of California was published in 1993, its Geographic Subdivisions of California map included an area of Klamath Ranges geology in its Cascade Ranges subdivision, creating an anomaly with floristic ramifications. We aim to correct that anomaly in this paper. This incorrect designation leads to several issues, including ecologic and geologic inconsistences, and problematic results when conducting floristic analysis in the eastern Klamath Ranges. Botanical field surveys for several recent projects in the eastern Klamath Ranges, newly available digitized data made available online by the Consortium of California Herbaria, and several new taxa recently published from the eastern Klamath Ranges provided means and rationale to make much-needed changes to the Klamath Ranges boundary. Using personal experience, existing ecologic and geologic references, and GIS analysis we revised the Klamath and Cascade Ranges boundaries, provided geographic range updates for over 230 plant taxa, and updated the existing California Geographic Subdivisions descriptions to reflect the boundary revisions. Herein we present the revised map boundary, describe our analysis and results, and provide floristic analysis made possible by the map revisions.