It was originally named "79" due to its approximate distance in miles from the coastal city of Savannah.

[1] During the Civil War, a site for a prisoner-of-war camp to house Union soldiers was chosen about five miles from Millen's Junction.

Prior to the arrival of Union forces, Confederate soldiers evacuated the Camp Lawton prisoners to Savannah.

Georgia State Route 17 passes through the center of the city, entering from the west as Winthrope Avenue and leaving to the south as Masonic Street.

State Route 21 bypasses Millen to the northeast, ending at US 25 at the northern city limit.

[5] As of the 2020 United States census, there were 2,966 people, 1,113 households, and 563 families residing in the city.