It's an incident that's become a part of Chicago lore.
Thursday marked 20 years since "poopgate," as the internet has dubbed it over the past two decades.
The disgusting event happened as the tour bus drove over the Kinzie Street Bridge in Downtown Chicago.
The bus dumped 800 pounds of bathroom waste into the river as unsuspecting passengers on an Architecture Foundation tour boat passed under the bridge.
ABC7 talked to a woman, Lynn LaPlante, who was driving behind the bus that day and drove right through the mess.
"The smell, I mean there was just no mistaking the smell," LaPlante said. "It was a lovely day, just driving windows open, perfect August day in Chicago, and we drove basically into just a wall of smell."
To commemorate the infamous brown shower, a memorial plaque was placed on the bridge to never forget the incident. Benny the Bull and other Chicago sports mascots visited the site Thursday to pay their respects, using toilet paper to wipe away tears.