Under the main part of the Lincoln Memorial (also known as the superstructure), sits a 43,800 square foot area called the Undercroft (a subterranean or ground-level room or vault beneath a building). The National Park Service has worked to build the new Lincoln Memorial Undercroft museum with support from The National Park Foundation and the Trust for the National Mall.

Rendering image courtesy of National Park Service. Cross section of the Lincoln Memorial showing the statue, chamber, and undercroft.

When the Lincoln Memorial was originally built between 1914 and 1922, the ground upon which it was constructed—called the Potomac Flats (sometimes known as the Kidwell Flats)—was marshland reclaimed from the Potomac River several years earlier. Due to the swampy and uneven nature of the ground beneath it, the Memorial was built atop 122 massive concrete pillars with a cavernous area beneath the main superstructure. Construction workers who built the Memorial left behind various objects which give archaeologists, historians, and other researchers a view of what construction on the National Mall’s most visited Memorial was like. Tools, bottles, workers’ clothing, and graffiti are among the primary sources generated from archaeological studies conducted in the Undercroft, much of which is on display in the exhibit space.

For President’s Day (and ahead of the NPS centennial) in 2016, philanthropist David Rubenstein made a 18.5-million-dollar donation to the National Park Foundation, to be used to repair, restore, and add accessibility features to the Lincoln Memorial, and for construction of the Lincoln Memorial Undercroft space. Construction on the 69-million-dollar project began in March 2023, and the museum opened to the public on June 25th, 2026. Visitors can expect a grand space in one of the few spaces on the National Mall that has been largely unseen by members of the public since the late 1980s.