Monitoring the spread and distribution of introduced species in an area can be challenging due to a variety of issues. Range expansion may exceed expected rates if the area of introduction is more suitable than expected, and may be slowed by an area in which it is difficult to establish a population. The species of interest in this study is the Eastern Fox Squirrel (Sciurus niger rufiventer) and the focus of the study is the spread of the species in Southern California. Previous studies have shown a steady and continuous spread from main points of introduction in Southern California and the species is now considered well established in the region. In this study, we collected and mapped new location data within Southern California. We discuss the spread of the Eastern Fox Squirrel in this area from 2005 through 2014 and include habitat suitability models to project the potential future distribution of the species. Results show that the Eastern Fox Squirrel has spread east into Rancho Cucamonga, into southern portions of Irvine, and has maintained isolated populations in places such as San Diego and Riverside. Our models suggest potential future paths of movement for contiguous range expansion.