Whidbey Island (historical spelling Whidby) is the largest of the islands composing Island County, Washington, in the United States. (The other large island is Camano Island, east of Whidbey.) Whidbey is about 30 miles (48 km) north of Seattle, and lies between the Olympic Peninsula and the I-5 corridor of western Washington. The island forms the northern boundary of Puget Sound.