Coupeville is a small seaport on Penn Cove, halfway up Whidbey Island, and one of Washington's most rewarding small-town stops. It sits inside Ebey's Landing National Historical Reserve, where old farms, prairie bluffs, military forts, and a Victorian waterfront have been protected as one lived-in landscape rather than a sealed museum.
The town is compact: Front Street, the wharf, a few blocks of old houses, and the cove where mussel rafts sit offshore. The wider reserve is the reason to stay longer. Trails climb above the water at Ebey's Landing, while Fort Casey State Park guards Admiralty Inlet a short drive south.
Coupeville is a very good spare-day trip from Seattle, Port Townsend, or anywhere on Whidbey. Come by ferry if you can; the crossing from Port Townsend makes the town feel properly maritime before you even arrive.