Before the World of the Dead
Fiddler's Green was once a great and beautiful city. It had the perfect location for commercial companies and industries but also a population of 2 million people.
After the World of the Dead
When the zombie epidemic was out of control by the government, a merchant called Kaufman took over the center of Fiddlers Green and made it a fortress called "City of the Living".
It was a ideal place to start over again, so Kaufman believed. Unfortunately he became corrupt, he split his people into two groups: the rich and the poor. Everyone who could afford a place in Kaufman's castle was perfectly safe from any threat and could get life support. The poor would be left for dead on the streets, they have to survive on their own. Some of them even have to go out in the nearby dead cities to get food for Kaufman.
In 1971 (three years after the first dead walk), the team who was sent out in the dead cities started to discover an intelligence present among the dead. Ignoring this possible threat, the City of the Living was eventually attacked by the zombies and is now (like most of the cities) a ravaged city.
Fiddler's Green was protected on two sides by rivers and the main roads and bridges to enter the city were completely sealed off by Kaufman's troops. While the land side of the peninsula was protected by a gigantic electric fence. Unknown to Kaufman, that zombies do not need oxygen and can simply walk under water right into the city which led to it's ultimate downfall.