The Puget Sound is a region in Washington.
Puget Sound is a sheltered arm of ocean between Seattle and the mainland of Washington State to the east and the Olympic Peninsula to the west. The southern boundary is marked by where the mainland and the Olympic Peninsula meet, near Tacoma. The northern boundary is marked by Admiralty Pass and the Strait of San Juan de Fuca. The San Juan Islands are, contrary to frequent belief, not in Puget Sound.
The Puget Sound region consists Puget Sound itself, the islands of Puget Sound, the Kitsap Peninsula, plus the mainland which forms the eastern boundary of Puget Sound. That is, it consists of Island, Snohomish, Kitsap, King, Pierce, and Thurston Counties.