It may have been named in 1788 by British Captain Charles Duncan after John Pitt, 2nd Earl of Chatham, who was First Lord of the Admiralty at that time.

[1][3] Chatham Sound is a semi-enclosed basin with an area of about 1,600 square kilometres (600 sq mi).

It is connected to the open waters of the Hecate Strait and Dixon Entrance via several channels, such as Main, Brown, Hudson Bay, and Edye Passages.

Because of the large inflow of fresh water the salinity of the sound is lower than the adjacent ocean.

[6] Currents are proportionately strong, and highly variable due to a combination of large tidal ranges, seasonally strong winds, and large peak freshwater discharges from the Skeena and Nass Rivers.