The Dead Lands by Benjamin Percy
As far as anyone knows, there is nothing beyond the walls of Sanctuary. It has been one hundred and fifty years since the flu virus mutated and the world fell apart and as far as the inhabitants of what was once downtown St. Louis, Missouri know, they are the only ones left.
At least that’s what they thought. From the wasteland beyond came a single rider bearing tales of a land where rain still falls, crops still grow, and mankind still thrives.
Against the wishes of the Sanctuary’s mayor, Ranger Mina Clark and museum curator Lewis Meriwhether depart the town in secret to lead a small band of explorers to follow the mysterious rider West.