GTA III Map Unlocks: Three Districts, Not Islands – Story Progression

GTA III doesn't have a "third island"—it has three districts unlocked via story progress:

1. Portland: Starting area.
2. Staunton Island: Unlocks mid-game after Portland missions.
3. Shoreside Vale: Final district, unlocks late-game after Staunton missions.

No fixed time; depends on your mission pace. The map opens gradually as you advance the story.