The shape of Portland’s peninsula changed dramatically over the past two hundred years as its shoreline was repeatedly reconfigured by in-filling. These composite maps, created by Rosemary Mosher with Geographic Information Systems (GIS) technology, combine historical maps with aerial photographs to retrace the peninsula’s expansion. Several major land fills extended the urban core into Portland Harbor and up the Fore River to support commercial and industrial enterprises. New residential property was created by filling in the Back Cove. The transportation network of streets, railroads, and interstate highways kept pace with the demands imposed by increasing population and accompanying real estate development.