Currently there are 1,908 active landfills across the United States; however, in the 1970s, prior to the modern era of sanitary landfills, there may have been as many as 100,000 landfills and dumps. Most of these landfills and dumps were unregulated and were abandoned, and details about their locations and characteristics are poorly documented. The Abandoned Landfill Inventory produced by the Pennsylvania Department of Environmental Protection lists 2,620 waste facilities in the state, of which 1,309 are described as “landfills” or “abandoned landfills.” There are 157 reported facilities in Lancaster County, PA. Seventeen are “landfills” or “abandoned landfills”; however, it is clear that most of the landfills and dumps that existed in Lancaster are not listed. A 1971 report documented approximately 23 land disposal sites, including eight landfills (one of which was a licensed sanitary landfill), 15 dumps, approximately 44 identified informal dumps, and perhaps 200 to 300 additional unidentified informal dumps. This study uses LIDAR and historical aerial photography integrated into a GIS database to investigate three dump sites in Lancaster County, PA. The sites had varying degrees of available information about their location and extent. The techniques discussed here can be used to investigate other ‘known’ and possible abandoned sites in order to significantly increase the robustness of the available data about these sites, leading to better monitoring and even remediation in extreme cases. As land-use pressures increase with an expanding population abandoned landfill sites need to be avoided or used in appropriate ways.