Phil Cassidy's Army Surplus
Staunton Island Military Base is a military base at the north of Rockford, Staunton Island in Liberty City, featured in Grand Theft Auto III. The base seems like a reserve warehouse, there are no military personal in there and you can freely enter it, although part of base fenced off by a moving gate.
In mission Arms Shortage you have to meet Phil Cassidy in this base; then you will defend it from the Colombian Cartel members. After that mission you can buy high powered "army grade" weapons here, such as Rocket Launcher. A Barracks OL is usually parked in here. If you have collected all 100 hidden packages, a Rhino will also appear here. If you have a wanted level, occasionally police cars, or higher law enforcement vehicles, will spawn halfway inside the wall of the building.