The eastern fox squirrel (Sciurus niger) is one of 22 non-native species of mammals now successfully breeding in the wild in California. The focus of this study was to describe current and historical distribution of the eastern fox squirrel in the greater Los Angeles metropolitan area (Los Angeles, Orange, and Ventura counties) in relation to their initial point of introduction in 1904. Data were obtained through questionnaires, submissions to websites, direct observations, records of wildlife-rehabilitation centers, and specimens in the Los Angeles County Museum of Natural History. Locations of eastern fox squirrels were geo-referenced on a map to ascertain the current distribution. A time-series distribution map was created to document expansion of the range from the point of introduction to distribution of the species in the greater Los Angeles metropolitan area as of 2004. Distribution of the population in Los Angeles County was expanding at rates of 0.44–3.44 km/year during varying time periods over the 100 years since the introduction. By determining the periphery of the current distribution of the eastern fox squirrel and rate of expansion of the range in the greater Los Angeles metropolitan area, wildlife managers in surrounding communities may be able to anticipate locations where future expansions of the range may occur.