Lake Union is a freshwater lake entirely within the Seattle, Washington city limits and a major portion of the Lake Washington Ship Canal. Its easternmost point is the Ship Canal Bridge, which carries Interstate 5 over the eastern arm of the lake and separates Lake Union from Portage Bay. Lake Union is the namesake of the neighborhoods located on its east and west shores: Eastlake and Westlake, respectively. The northern shore of the lake is home to Gas Works Park. Notable features of the southern portion of the lake—collectively known as the South Lake Union district—include Lake Union Park, Museum of History & Industry and the Center for Wooden Boats.
The George Washington Memorial "Aurora" Bridge carries State Route 99 over the western arm of Lake Union. The Aurora Bridge is so named because it carries Aurora Ave N down the western side of the lake. Lake Union's westernmost point can be considered the Fremont Cut, which is located just east of the Aurora Bridge and is spanned by the Fremont Bridge. The Fremont Bridge carries Fremont Ave N between the neighborhoods of Fremont and Queen Anne and separates Lake Union from the rest of the Lake Washington Ship Canal to the west.