The strait is between 2.5 km and 5 km wide. It is a major navigation channel on the west coast of North America. It is the preferred channel for vessels from the Georgia Strait leaving to the north of Vancouver Island through the Queen Charlotte Strait bound for Prince Rupert, Queen Charlotte Islands, Alaska, and the North Pacific Ocean, and for southbound vessels from those areas bound for the Port of Vancouver.
The Strait is home to approximately 150 orca whales during the summer months, which are often seen by kayakers and boaters packed with tourists. Scientists including Michael Bigg and Paul Spong have been researching the orcas in the Strait since 1970. Spong established the OrcaLab, based on studying the Orcas in their natural habitat without interfering with their lives or their habitat. The strait includes the Robson Bight Ecological Reserve.
The Strait was named by Vancouver for James Johnstone, master of the armed tender Chatham. In 1792, his survey party established that Vancouver Island was an island.
There are no cities or towns along the length of the strait. Telegraph Cove and Robson Bight on Vancouver Island are along the strait near its north end and the village of Sayward on Kelsey Bay is near its midpoint.