Lake Shannon is a long, narrow reservoir on the Baker River in Skagit County, Washington in the United States.

Located just outside the western boundary of North Cascades National Park, Lake Shannon serves as the lower reservoir for Puget Sound Energy's Baker River Hydroelectric Project.

An artificial fish passage system was begun in the 1950s and completed in 1959 after the construction of Upper Baker Dam, located upstream of Lake Shannon.

[5] The dominant geographical feature in the area is Mount Baker, which rises 10,781 feet (3,286 m) a few miles to the northwest of Lake Shannon.

Large deposits of lime around the mouth of the Baker River were taken advantage of by a cement plant built in present-day Concrete.

[9] On April 1, 1924,[10] the Lower Baker Dam was official begun by the Stone & Webster Company, in a site known as Eden Canyon.

[11] In early 1925, the Lower Baker Dam was completed to a height of 230 feet (70 m) by a construction crew of 1,300, and in November of that year, the reservoir first filled to capacity.

[15] On July 9, 1959, Upper Baker Dam was completed and the inflow to Lake Shannon became regulated for the first time.

True kokanees are established in freshwater, but the kokanees of Lake Shannon may be the by-product of sockeye salmon and coho salmon that spawned in tributaries of the lake — including Sulphur Creek and Thunder Creek — either via natural spawining gravels or artificially constructed ones.

Some of the fry escaped the conduits that carry outmigrating young salmon into the lower Baker and the Skagit, establishing a population of kokanee.

However, the only access to the Lake Shannon boat launch area involves passing through privately owned land.

[18] There are plans to extend the current hiking trail system surrounding the two reservoirs by 8 miles (13 km)[20][21] and other general improvements within the hydroelectric project area.