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]
Outdated - the smell is mostly gone now. Based on timing of when the pulp mill closed, it seems to have been the main cause.
This is the correct answer, it was the pulp mill.
A friend of mine made up a rap song a long time ago about a superhero who got his powers from toxic waste. I remember one line, “His stupefying aroma, is like he’s from Tacoma.”
There was a paper towel/toilet paper factory in my college town and yeah woof everyone knew it when they were in the area.