Open to the public and free of charge, the museum was privately established in 1937 for the American people by a joint resolution of the United States Congress.

Andrew W. Mellon, Pittsburgh banker and Treasury Secretary from 1921 until 1932, began gathering a private collection of old master paintings and sculptures during World War I.

[citation needed] In 1929 Mellon had initiated contact with the recently appointed Secretary of the Smithsonian Institution, Charles Greeley Abbot.

When the director of the Gallery retired, Mellon asked Abbot not to appoint a successor, as he proposed to endow a new building with funds for expansion of the collections.

[citation needed] However, Mellon's trial for tax evasion, centering on the Trust and the Hermitage paintings, caused the plan to be modified.

When asked by Abbot, he explained that the project was in the hands of the Trust and that its decisions were partly dependent on "the attitude of the Government towards the gift".

On his birthday, 24 March 1937, an Act of Congress accepted the collection and building funds (provided through the Trust), and approved the construction of a museum on the National Mall.

[6] Designed by architect John Russell Pope, the new structure was completed and accepted by President Franklin D. Roosevelt on behalf of the American people on March 17, 1941.

[5] As anticipated by Mellon, the creation of the National Gallery encouraged the donation of other substantial art collections by a number of private donors.

Designed by architect I. M. Pei, the contemporary structure was completed in 1978 and was opened on June 1 of that year by President Jimmy Carter.

The new building was built to house the Museum's collection of modern paintings, drawings, sculptures, and prints, as well as study and research centers and offices.

Completed and opened to the public on May 23, 1999, the location provides an outdoor setting for exhibiting a number of large pieces from the Museum's contemporary sculpture collection.

As part of the celebration of the reopening of this wing, organist Alexander Frey performed 4 sold-out recitals of music of France in one weekend in the French Gallery.

The United States federal government provides funds, through annual appropriations, to support the museum's operations and maintenance.

[8][9] The museum hired Evelyn Carmen Ramos, the first woman and the first person of color to be the chief curatorial and conservation officer, in 2021.

Extending east and west from the rotunda, a pair of skylit sculpture halls provide its main circulation spine.

In contrast, the design of the East Building, by architect I. M. Pei, is geometrical, dividing the trapezoidal shape of the site into two triangles: one contains public galleries, and the other houses a library, offices, and a study center.

The East Building's central feature is a high atrium designed as an open interior court that is enclosed by a sculptural space spanning 16,000 sq ft (1,500 m2).

The East Building also contains the main offices of the NGA and a large research facility, Center for Advanced Study in the Visual Arts (CASVA).

The Sculpture Garden contains plantings of Native American species of canopy and flowering trees, shrubs, ground covers, and perennials.

A circular reflecting pool and fountain form the center of its design, which arching pathways of granite and crushed stone complement.

[27] After congressional testimony that the East Building suffered from "systematic structural failures", NGA adopted a Master Renovations Plan in 1999.

[28] A group of benefactors — which included Victoria and Roger Sant, Mitchell and Emily Rales, and David Rubenstein — privately financed the renovation.

Plans for renovating conservation, construction, exhibition prep, groundskeeping, office, storage, and other internal facilities were also ready, but would not be implemented for many years.

The Italian Renaissance collection includes two panels from Duccio's Maesta, the tondo of the Adoration of the Magi by Fra Angelico and Filippo Lippi, a Botticelli work on the same subject, Giorgione's Allendale Nativity, Giovanni Bellini's The Feast of the Gods, Ginevra de' Benci (the only painting by Leonardo da Vinci in the Americas) and groups of works by Titian and Raphael.

The collections include paintings by many European masters, including a version of Saint Martin and the Beggar, by El Greco, and works by Matthias Grünewald, Cranach the Elder, Rogier van der Weyden, Albrecht Dürer, Frans Hals, Rembrandt, Johannes Vermeer, Francisco Goya, Jean Auguste Dominique Ingres, and Eugène Delacroix, among others.

It includes collections of works by Albrecht Dürer, Rembrandt, Giovanni Battista Piranesi, William Blake, Mary Cassatt, Edvard Munch, Jasper Johns, and Robert Rauschenberg.

[32] In 2013, the NGA purchased from a private French collection Gerard van Honthorst's 1623 painting, The Concert, which had not been publicly viewed since 1795.