Abstract Throughout the nineteenth century and the early part of the twentieth, the involvement of geologists in legal matters as part of their normal professional services was rare. A geologist’s principal endeavors prior to the early 1900s were mainly restricted to the more classical and academic studies of the Earth’s features and resources. An exception, and one of the earliest recorded cases of geological litigation and the as-encountered site conditions, involved excavation to enlarge the Erie Canal Locks at Lockport, New York, in 1839. James Hall of the New York Geological Survey was asked to evaluate and classify a “Slate Rock and Shale” sequence; the engineer’s contract quoted a unit price for “solid rock” and a lower price for “Slate Rock and Shale” (described in Chapter 1, this volume). Terms of the 1839 contract made a clear distinction between the rock types impossible. Even the early applied geologists (Chapter 1, this volume) were mainly involved with collecting and describing the geologic setting of a proposed project and providing the relevant information on areal and site maps with accompanying texts that described the general geologic conditions to be expected. Only on rare occasions would the highly respected early applied geologists, such as W. O. Crosby, James Kemp, Heinrich Ries, Charles P. Berkey, or Warren J. Mead, be invited to serve in litigation, and never as part of a large-scale claim or changed-conditions argument so common since the 1960s. Rather, those early applications of geology for legal purposes were usually restricted to a single geologic entity, such as the two detective problems of a geological flavor in the early 1900s solved by Professor Berkey: