RTF recently acquired a job in Allegany County which borders the Pennsylvania state line. It was very interesting and rewarding to work with some of the most historical survey markers in the United States. The Mason-Dixon Line was originally surveyed by Charles Mason and Jeremiah Dixon in the 1760’s. The Mason-Dixon Line forms a demarcation line among the borders of Maryland, Pennsylvania, West Virginia and Delaware. Ultimately, this significant part of U.S. surveying history denotes the boundary between the Northern and Southern United States.