Eight new apatite fission track (AFT) analyses from the Queen Charlotte Basin, British Columbia, reveal three distinct periods of cooling. The basin formed as the result of regional extension, as the North American plate boundary transitioned from a continental subduction zone to a transform margin. Samples were collected from localities across two major normal faults, the Grenville Channel fault and Principe Laredo fault. This study uses AFT analyses, which document the thermal histories of rocks from ~130-60?C, to examine the extensional history of the basin. Three groups of AFT ages can be interpreted to represent three separate stages of extension, beginning with the initial transition in plate boundary type at ~51-45 Ma, then continuing with extension accommodated by normal faulting from ~32-34 Ma, followed by volcanism in the most recent stage of development, ~17-19 Ma. The opening of the Queen Charlotte Basin lasted for a long period of time, ~30 million years, with distinct periods of faulting and volcanism, as proposed by Rusmore et al., ( in review ). This study offers a more complete model for the opening of the Queen Charlotte Basin.