The origins of the collection of marine invertebrates under the care of the Smithsonian Institution can be traced to the collections made by William Stimpson while serving as zoologist on the North Pacific Exploring Expedition, 1853-1856, and the specimens collected by the United States Exploring Expedition, which were transferred to the Smithsonian in 1858. Stimpson seems to have been, nominally at least, in charge of the Smithsonian marine invertebrate collections until 1865. By that date the Smithsonian collection of crustacea numbered more than 10,000 jars - the largest in the world at that time. Beginning in the 1870s, large collections of marine invertebrates came to the Smithsonian as a result of the various expeditions conducted by the U. S. Fish Commission. Many of these specimens were retained at Yale University by Addison Emery Verrill for study and identification and did not reach the United States National Museum until 1907.
As a result of a general reorganization of the United States National Museum, the Department of Marine Invertebrates was established in 1880. Under its care were all recent invertebrates, marine and aquatic (excepting mollusks and insects), including protozoans, sponges, coelenterates, echinoderms, ascidians, worms, bryozoans, and crustaceans. Richard Rathbun (1852-1918), a scientific assistant with the U. S. Fish Commission, was appointed honorary curator of Marine Invertebrates in 1880 and retained the title until 1914. In 1897, he was appointed assistant secretary of the Smithsonian Institution, and responsibility for the administration of the Division of Marine Invertebrates fell largely on the two assistant curators, James E. Benedict and Mary Jane Rathbun.
Prior to his appointment as assistant curator in 1890, James F. Benedict (1854-1930) had served as naturalist on the U. S. Fish Commission steamer Albatross. He continued his duties in the Division of Marine Invertebrates until 1909 when he accepted appointment as Chief of Exhibits in the Department of Biology, United States National Museum (USNM).
Mary Jane Rathbun (1860-1943), a sister of Richard Rathbun, was appointed copyist in the Department of Marine Invertebrates in 1886. She was promoted to aid in 1893 and assistant curator in 1894. After her resignation in 1914, she was given the honorary title associate in zoology, and she remained in close association with the museum until her death in 1943.
In 1897 USNM was reorganized into three departments: Biology, Geology, and Anthropology, with Marine Invertebrates as a division of the Department of Biology. On October 16, 1914, the Division of Marine Invertebrates was merged with the Division of Mollusks into a single division under the former title. Richard Rathbun resigned as curator, and the position was assumed by Paul Bartsch. The collection of echinoderms was removed from the Division of Marine Invertebrates on April 1, 1919, and a separate Division of Echinoderms was created with Austin H. Clark as curator. Clark had served as assistant curator in the Division of Marine Invertebrates since 1909. On February 1, 1921 the collections of mollusks were removed from the Division of Marine Invertebrates, and the Division of Mollusks was reestablished with Paul Bartsch as curator. Waldo LaSalle Schmitt assumed the curatorship of the Division of Marine Invertebrates.
In 1947 another administrative reorganization took place in the USNM. As part of the reorganization, the Department of Biology was divided into Departments of Botany and Zoology, with Marine Invertebrates becoming a division of the Department of Zoology. In 1964 the Department of Zoology was divided into three departments: Vertebrate Zoology, Invertebrate Zoology, and Entomology, with Marine Invertebrates a division of the Department of Invertebrate Zoology. On July 1, 1965 the Division of Marine Invertebrates was abolished and three new divisions were formed - Crustacea, Echinoderms, and Worms - and were joined with the existing Division of Mollusks to form the Department of Invertebrate Zoology.