The major advances made in the design and operation of transfer pumps (i.e. vacuum pumps that transfer gas from a vacuum system to the atmosphere) during the lifetime of the American Vacuum Society (1953-2003) are reviewed. Included are vapor-jet, turbomolecular, and oil-free mechanical pumps. In addition to engineering development of pump designs, the basic understanding of pumping mechanisms of various pumps and their performance parameters has been greatly improved during this period.