The town whose population was around 3,450 was a quiet suburban community whose residents happily lived their day-to-day routines until these were destroyed by The Infection. Riverside is centered on its Main Street which betrays its 18th- or 19th-Century origins whilst following a typical contemporary American small town strip development with an eclectic mix of retail stores, low-rise office and commercial buildings and a movie theater.
After the Infection broke out, the U.S. Military attempted to convert the town into a safe point working alongside the media trying to inform the public. In default of "a better plan," the Survivors decide to strike out for Riverside and their journey to this town forms the basis of both the Crash Course and Death Toll campaigns. Unfortunately, Riverside has been overrun by the time the Survivors get there. To their dismay, they find that not only has the military abandoned the town, but many of its personnel have become infected and form a significant component of the Common Infected now occupying the place. A notable aspect of Riverside is the Valley Church at which the Survivors make the acquaintance of the ever-paranoid "Church Guy" who has cracked under the psychological pressure and been "bitten" by an Infected. One way or another, he ends up ringing the church bell which triggers a Crescendo Event and obliges the Survivors to fight for their lives against waves of the Common and Special Infected. Riverside itself is densely populated with Common and Special Infected―including at least one Tank and Witch. The aforementioned Main Street was evidently designated a key defense point by the military and they set up a fixed machine gun and even went so far as to use combat engineers to build a vast earth and rubble barrier across the street.
There is a real Riverside located in Pennsylvania with a population of 2,000, which is similar to the Riverside in Left 4 Dead.
Despite its hinted location somewhere in Pennsylvania, this town seems to be modeled after Riverside, California. The church and the graveyard as well as Riverside Park are images taken right from this Californian town.
CEDA refers to Valley Church as the Riverside First Church during the evacuation of Whitney County and the city of Fairfield (as seen in the CEDA posters).
One of the last remaining survivors of Riverside was probably the Church Guy who finally succumbed to the infection.
Zoey has been to Riverside before as when the Survivors are in the town and come to the main street (next to the movie theater) she will comment, "I always liked this main street."
The pharmacy store is well known throughout the tri-state area as several advertisements in different cities inform the public to shop at this store and purchase its well known Pills. However, the Survivors never actually see the store in the town.