SEATTLE — The Fourth of July is more than Independence Day — it also marks the birthday of the Ballard Locks, which are 96 years old.
When the locks first opened in 1917, they created the first link between the freshwaters of Lake Union and Lake Washington and the saltwater of Puget Sound.
Part of their job is to prevent the two types of water from mixing in order to preserve the delicate freshwater ecosystem. They also move commercial and pleasure boats from the water level of the sound to that of the lakes.
There are two locks, one small and one large and a fish ladder for salmon. Lake Washington and Lake Union are 22 feet above sea level.
More than a million tons of cargo, fuel, building materials and seafood products pass through the locks every year.