Jason Isbell and the 400 Unit is a band led by former Drive-By Truckers singer and guitarist Jason Isbell. It includes guitarist Sadler Vaden, bassist Jimbo Hart, keyboardist Derry DeBorja, drummer Chad Gamble, and Amanda Shires on fiddle and frequent harmony vocals.

The 400 Unit is named after the psychiatric ward at Eliza Coffee Memorial Hospital in Florence, Alabama.

Their first album, Jason Isbell and the 400 unit, was released in 2009. Their second album, Here We Rest was released in April of 2011.

These two albums followed Isbell’s solo debut, Sirens in the Ditch, which came out just three months after his split from Drive-By Truckers and without “the 400 Unit.” In the years following Here We Rest, Isbell rose to significant commercial and critical success behind behind albums Southeastern and Something More Than Free.

The band thus released their third album, The Nashville Sound to much greater fanfare and success, reaching #1 on the US Country, Folk, Rock, and Indie charts in the fall of 2017.