United States Botanic Garden
Botanical Garden

Courtesy of U.S. Botanic Garden
Established nearly two centuries ago in 1820, the United States Botanic Garden is one of the oldest botanical gardens in the country. Grounded in Washington, D.C., just a stone’s throw from the Capitol, the garden comprises roughly 65,000 plants, including species which date back to the 19th century. Happily, for history (and horticulture!) buffs, the garden boasts free admission.