Like so many communities settled in the 1800s, Justin's growth was linked to that of the railway. Situated in southwestern Denton County, the area was originally settled by a band of French colonists. The community was abandoned a year later, and the area remained sparsely populated until the 1880s, when residents and businesses came to the area along with the Santa Fe Railway.
Residents of nearby Roanoke, Elizabeth, and Drop moved to be near the railroad. In January 1887 the community petitioned postal authorities for a post office to be named Justin, in honor of Justin Sherman, chief engineer of the Santa Fe line. The community benefited from prosperous wheat and dairy farms. It eventually grew to include a general store, a grocery, a hotel, a cotton gin, grain elevators, frozen food lockers, paved roads, a movie theater, a weekly newspaper, and a prep school.
According to the 2000 census, the median household income in Justin was $52,257 and media home value was $105,300. Homes range from less than $100,000 to $800,000 and include everything from manufactured housing to custom estates.