The plant collections of the Smithsonian Institution began with the acquisition of specimens collected by the United States Exploring Expedition (1838-1842). These formed the foundation of a national herbarium which today numbers 4.8 million historical plant records, placing it among the world's largest and most important.

See: http://www.mnh.si.edu/rc/db/2data_access_policy.html

See: http://www.mnh.si.edu/rc/db/collection_db_policy1.html