Quahog Harbor is a major port-of-entry for shipping in Quahog.
The family smuggle themselves back from Italy through the harbor by posing as sex dolls in "Boopa-Dee Bappa-Dee".
Quagmire buys a condo at Prescott Towers from Brian in "Brian the Closer", only to discover that it is a run-down dump as a neighbor warns him that the harbor is poisoned.
When Peter is caught by Joe with possible child porn on his laptop computer in "The 2000-Year-Old Virgin", he rushes the laptop to the harbor and dumps it far offshore.
In "Island Adventure", Stewie tows 'garbage island' to Quahog Harbor rather than leave Brian behind.