While it’s currently the National Portrait Gallery and the Smithsonian American Art Museum, the Old Patent Office reflects an era when scientific invention propelled the American economy and began to mold the national character. Although more than a half million patents were issued here, the building was designed not just to house patent examiners, but also to display the models required for patent applications. Throughout the nineteenth century, the Patent Office was an important public attraction, exhibiting the Declaration of Independence, art collections of the National Institute, and other historical artifacts as well. During the Civil War, the building served as a temporary barracks and hospital; Walt Whitman’s nursing here gave inspiration to his poetry. It was also the site of Lincoln’s second inaugural ball. A century later, the building’s rescue contributed significantly to the development of the historic preservation movement and the assumption of federal responsibility for stewardship of historic landmarks. The General Services Administration contemplated demolition of the building for a parking garage in the late 1950s, but President Eisenhower intervened, and in 1962, Congress turned the building over to the Smithsonian for museum use. It was renovated in between 1964 and 1967 and reopened to the public in 1968. Although most of the interior has been altered for use as a museum, parts of the Old Patent Office interior are still visible on the building’s third floor in the National Portrait Gallery’s Great Hall. DC Inventory: November 8, 1964 (Joint Committee on Landmarks)

The original National Observatory was authorized by President Tyler in 1842 and completed in 1844 according to plans prepared by Lieutenant James Melville Gilliss. The observatory was the site of notable advances in astronomy and mathematics, and is associated with its first superintendent, Matthew Fontaine Maury, who supervised the publication of numerous volumes of oceanographical charts, and was the author of the first oceanographical textbook. The observatory installed a new transit circle instrument by the end of the Civil War. The domed south wing housed the 26-inch Great Equatorial telescope, the largest of its day, installed in 1873. In 1877, astronomer Asaph Hall discovered the moons of Mars with this instrument.

From its inception, the observatory was authorized to calculate and keep official time, which was indicated by the dropping of a time ball from the flagstaff each day at noon. By 1878, poor atmospheric conditions in Foggy Bottom led Congress to authorize relocation to a new site, and in 1893, the observatory moved to its new home on Massachusetts Avenue. After its relocation, the property was transferred to the Navy’s Bureau of Medicine and Surgery to serve as a Museum of Hygiene, and later the Naval Medical School.

DC Inventory: November 8, 1964 (Joint Committee on Landmarks)

National Register: October 15, 1966

National Historic Landmark: January 12, 1965

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Founded in 1880, the original Library of Congress collection included 740 books and three maps. This collection lived in the Capitol until 1814, when invading British troops burned the Capitol and destroyed the library inside it. Former President Thomas Jefferson subsequently sold his personal collection of 6,487 books to the government, which became the foundation of the present-day Library of Congress. The Library's main building is named for Jefferson in recognition of the importance of his collection.

Although originally designated for the needs of Congress only, the Library of Congress' audience grew to include all government agencies, serious scholars, other libraries and the general public, and the collections have grown accordingly. The Library's holdings had expanded to such a degree by 1881 that it was apparent that a dedicated building was needed. The imposing, Beaux-Arts style Jefferson Building was constructed between 1886 and 1897. With its continuously expanding collections and activities now spread across multiple buildings,* the Library of Congress is the world's largest library, with more than 167 million items in around 470 languages.

*Although not historically-designated, the Library of Congress also encompasses the Art Deco style John Adams Building (1938) and the modernist James Madison Memorial Building (1980).

DC Inventory: November 8, 1964 (Joint Committee on Landmarks)

National Historic Landmark: December 21, 1965

Exempt from National Register listing (per Section 107 of the National Historic Preservation Act of 1966)

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