Justin is located at the intersection of Farm roads 407 and 156, five miles northwest of Grapevine Lake in southwestern Denton County.
It is just northwest of the Dallas, Texas metro area.
The town's population increased from 476 in 1904 to 700 in 1941, and in 1947 Justin was incorporated. In 1980 the population was reported as 920. During the 1980s many residents commuted on I-35 to jobs in nearby Denton and Fort Worth.
In 1987 the Flying S Farm airstrip was located just outside the town. In 1990 Justin reported a population of 1,282 and seventy-six businesses.