Established in New York City in April 1876, the American Chemical Society is an education and professional society for chemists and chemical engineers. With more than 110,000 members, it sponsors numerous activities designed to foster the cultivation and diffusion of chemical knowledge in all areas of American society. The stamp design has a great deal of detail: a modern alembic with supporting instruments, the conventional hydrometer, and modern ionization indicator; and to the right is the horizon of the chemical century, typified by the towers of the catalytic cracking plant, a butadiene reactor, and a fractionating unit.