Northern Straits is a Salishan language within the Coast Salish branch.

Klallam and Northern Straits are very closely related, but have lost mutual intelligibility.

[2] Historians have historically classified the various dialects of Northern Straits and Klallam together in many ways.

German anthropologist Franz Boas believed that Klallam was part of the same language as Northern Straits.

Despite this, Klallam and the dialects of Northern Straits Salish are not mutually intelligible.