What is the oldest tree in Washington DC?

Age and documentation are different things in Washington, and the distinction shapes this whole list. Most cities on this site guess at their oldest tree from girth and legend; Washington can often simply look it up. The Architect of the Capitol has recorded plantings on the Capitol grounds since the Olmsted landscape was laid out, which is how the Grant Memorial Bur Oak's seniority over its own memorial is a matter of record rather than estimate. The National Park Service goes further and keeps a formal register of witness trees, individuals that stood through documented history, from the mulberry that predates the Washington Monument's completion to the elm whose cuttings became the disease-resistant Jefferson cultivar planted across the country. Even the champion chestnut oak in Battery Kemble Park, the city's largest tree, carries an official co-champion designation with measurements behind it. None of these trees rivals a European yew for age. What they offer instead is certainty, and for a project built on verification, a 150-year-old tree with a planting ledger can be a better tree than a 500-year-old one with a story.