Mates of State is a duo consisting of Kori Gardner and Jason Hammel, who are also husband and wife. Gardner and Hammel met in Lawrence, KS, moved to California in 1998, and married in 2001.

The early music of Mates of State featured drums and the electric organ almost exclusively. On later recordings, additional instrumentation is included. Vocal harmony between Gardner and Hammel is a key feature of the music, as well as unusual rhythms and song structure.

Their first album was released on Omnibus Records; the second and third on Polyvinyl. In 2005, they moved to Barsuk Records.