Jason Isbell And The 400 Unit has been played on NTS shows including Country Hayride, with Codeine first played on 2 June 2019.

Jason Isbell and the 400 Unit is an Americana / Southern rock band originating largely from the Muscle Shoals area of Alabama, and led by former Drive-by Truckers singer / guitarist Jason Isbell.

The band consists of Isbell (vocals, guitar); Sadler Vaden (guitar); Jimbo Hart (bass); Derry DeBorja (keys, accordion); Chad Gamble (drums).

Fiddle player and singer Amanda Shires features regularly as a session player and occasional touring member.

The band is named for the colloquial name of the psychiatric ward of Eliza Coffee Memorial Hospital in Florence, Alabama.

The band are credited as such on five of Isbell's eight studio full-lengths, Jason Isbell and the 400 Unit (2009); Here We Rest (2011); The Nashville Sound (2017); Reunions (2020); Weathervanes (2023). Though some or all of the members feature on Jason's three "solo" albums, 2007's Sirens of the Ditch, his 2013 breakthrough Southeastern, and 2015's Something More Than Free.

The band tour regularly in the United States and internationally, including and annual week of shows at Nashville's legendary Ryman Auditorium supported by Shires and a variety of up and coming country, folk, and soul artists.