Jacqui asked: << Also, When did part of Chester Co., become part of New Castle Co., Delaware? >> To my knowledge, the only part was "the wedge," a triangular tract of several hundred acres that extended south of the east-west Mason-Dixon line, between the eastern boundary of Maryland and the 12-mile not-quite-circular boundary between Delaware and Pennsylvania. It went to Delaware by agreement between the states in 1921, after a resurvey of the circular boundary, the exact location of which had long been in doubt, placed in Pennsylvania a strip along it previously thought to be in Delaware. Donn Devine, CG, CGI Wilmington DE CG, Certified Genealogist, CGI, and Certified Genealogical Instructor are service marks of the Board for Certification of Genealogists, used under license by board certificants after periodic evaluation, and the board name is registered in the US Patent & Trademark Office.