The United States Department of Agriculture (USDA) has maintained herbarium collections since the establishment of the Department in 1862. Plant and seed material of crop or economically important species was of particular interest early on, and scientists began collecting and preserving these samples to document agricultural explorations and crop improvement studies. Over the next century, these collections grew in size and scope and were relocated several times, finally coming to the U.S. National Arboretum permanently in 1964.

The United States National Arboretum Herbarium houses around 700,000 specimens, approximately 25% of which are from cultivated, rather than wild, plants. This emphasis on cultivated material makes the herbarium here unique; it is one of the largest such collections in the United States and the world.