Lake Jacksonville is in the Neches River basin one-half mile southwest of Jacksonville in Cherokee County (centered at a point 31°55' N, 95°18' W). The city of Jacksonville began blocking up Gum Creek in February 1956 and completed the Lake Jacksonville dam in June 1959. The city owns the lake and uses it as a municipal water supply and recreational area.
The lake's capacity is normally 30,500 acre-feet, and its surface area at 422 feet above sea level is 1,320 acres. In emergencies the reservoir can be expanded to 46,500 acre-feet with a surface area of 1,760 acres. The lake has a drainage area of forty-one square miles. The soil around Lake Jacksonville is a sandy loam over red clay, and the area is wooded with mixed hardwood and pine trees.