The American Elm cultivar Ulmus americana 'Jefferson' was cloned from a tree growing near a path in front of the Freer Gallery of Art, close to the Smithsonian Institution Building ("The Castle") on the National Mall in Washington, D.C.[1] The United States National Park Service, which had planted the tree during the 1930s, cloned it in 1993 after screening tests showed that it possessed an outstanding level of tolerance to Dutch elm disease (DED).

[3] A genetic study that the ARS conducted on the clone at the United States National Arboretum in Washington, D. C., during 2004 confirmed the tree as Ulmus americana, despite having some atypical features.

[6] NA 62001 showed little damage from elm leaf beetle (Xanthogaleruca luteola) feeding during a 2009—2010 survey at an Oklahoma arboretum.

[7] 'Jefferson' is susceptible to elm yellows phytoplasma infection, as are other U. americana DED-resistant cultivars and native trees of that species.

[10] 'Jefferson' has not been widely tested beyond Washington D.C. National Elm Trial results were inconclusive and provided no data on ‘Jefferson’ because of an early error in tree identification that occurred in the nursery trade.