I saw this article at BoingBoing, and had to look it up.
From Wikipedia:
The Aroma of Tacoma, also known as the Tacoma Aroma, is a putrid and unpleasant odor associated with Tacoma, Washington, United States.[1] The smell has been described as similar to the odor of rotten eggs.[2] The odor is not noticeable throughout the city, but is rather concentrated in the Tacoma tideflats and is frequently smelled by motorists traveling that section of Interstate 5.[2]
In Shadowrun, they’ve merged. Not being American myself, I was surprised to discover they were actually distinct cities!
They are pretty much connected with the suburban areas between them. Driving on the freeway it’s like patches of purposely reserved green spaces but you could easily drive from one to the other in a couple hours by regular roads with business buildings along the way