Before the Great War, it was a productive port for fishing and boating with the Jefferson Memorial in its center. When the bombs fell, mirelurks began colonizing it, soon infesting the water. The basin is filled with many row boats, tugboats, and dinghies. Many boxes of loot are still aboard the half-sunken and dilapidated boats that mar in the shallows of the district's port basin.
Its surrounding territory was being fought over by the Brotherhood of Steel, the Enclave, and the super mutant hordes that occupied downtown Washington, D.C.. In 2277 the Brotherhood seized it and gained control of Project Purity. The Tidal Basin can be infected with the modified FEV if the Lone Wanderer chose to do so during Project Impurity.
- After completing the quest Take it Back!, there are a few Brotherhood of Steel initiates burning dead mirelurks with flamers in this location.
- After completing Take it Back! the water in the basin will no longer be irradiated.
The Tidal Basin appears only in Fallout 3.