The eastern fox squirrel, Sciurus niger, has been introduced to many areas outside of its native range. Once introduced to a new region the species has generally expanded its geographic range and is considered to be an invasive species, causing both ecological and economic harm. While some information is available on where introductions have occurred, detailed information is not available on the current geographic distribution of the species within California. Since invasive species tend to be under-represented in specimen collections at museums, new methods for obtaining location data were needed. We used a time period of 1995 through 2015 for observations so that location data would be most up-to-date. A majority (51%) of location data used in this study came from wildlife rehabilitation centers, approximately 31% came from citizen-science type sources such as the California Road-Kill Observation System, a previously published journal article, and research-grade submissions to iNaturalist, 10% came from the California Department of Public Health West Nile Virus Surveillance Program, and 8% came from the authors and trained student observers. Maps are presented to show the current geographic distribution of the species indicating a broader range than what was previously known.