The American Dispensatory, authored by John King and first published in 1876, stands as a monumental work in the field of Eclectic medicine. Spanning over 1,400 pages, this comprehensive reference book offers an extensive compilation of medicinal substances, including plant-based remedies, minerals, and animal products, along with their therapeutic applications, preparation methods, and dosages. The Dispensatory reflects the Eclectic movement’s ethos of integrating traditional herbal knowledge with emerging scientific understanding, serving as a vital resource for practitioners of the time.​

The content is meticulously organized into sections that detail the botanical characteristics, habitats, and cultivation methods of medicinal plants. It also covers the chemical composition of various drugs and provides instructions for preparing pharmaceutical formulations such as tinctures, extracts, pills, and ointments. Each entry includes therapeutic indications, dosages, and cautionary advice, emphasizing safety in medical treatment. This structured approach ensures that the Dispensatory is not only a catalog of substances but also a practical guide for their application in medical practice.​

While the Eclectic medicine movement has largely been supplanted by modern medical practices, The American Dispensatory remains an invaluable historical document. It offers insights into the medical knowledge and practices of the 19th century, preserving the legacy of botanical medicine and its role in American healthcare. For contemporary herbalists, researchers, and historians, it serves as a window into the evolution of medical treatment strategies and the enduring significance of plant-based remedies in healing traditions.