When a young, enthusiastic Asa Gray came to Cambridge in 1842, he brought with him a small but significant collection of herbarium specimens. Some twenty years later, he bequeathed that collection, then numbering some 200,000, to Harvard University. The subsequent growth and direction of “Gray's Herbarium,” and its transformations to the Gray Herbarium and the Harvard University Herbaria, are discussed with respect to five of its Curators and Directors: Sereno Watson, Benjamin L. Robinson, Charles A. Weatherby, Merritt L. Fernald, and Reed C. Rollins.