Milan is the second largest city after Humboldt in Gibson County, Tennessee and the largest entirely within the county. It is home to th…Milan is the second largest city after Humboldt in Gibson County, Tennessee and the largest entirely within the county. It is home to the Milan Army Ammunition Plant, the West Tennessee Agricultural Museum and several historical sites listed on the National Register of Historic Places. The city was the first in Tennessee to begin no-till farming and to fluoridate its drinking water. The Milan Endowment for Growth in Academics was the first private community financial endowment for public schools in Tennessee.