Thanks to British chemist James Smithson's generous bequest, Congress passed legislation establishing the Smithsonian Institution on August 10, 1846, in Washington, DC. Four years after establishing the Smithsonian, the population of Washington, DC, was 51,687. In 2025, an estimated 693,645 people lived in the nation's capital.

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The Smithsonian Institution was established thanks to the generous bequest of James Smithson, a British chemist and mineralogist and son of Hugh Percy (formerly Hugh Smithson), 1st Duke of Northumberland, and Elizabeth Hungerford Keate Macie. Smithson never married and had no children, leaving no heirs to inherit his estate following his death on June 27, 1829. Despite having never visited the United States, Smithson left his fortune "...to the United States of America, to found at Washington, under the name of the Smithsonian Institution, an establishment for the increase and diffusion of knowledge among men." 

On July 1, 1836, Congress passed "An Act to Authorize the President of the United States to Accept for the United States a Legacy Bequeathed by James Smithson." President Andrew Jackson [Page 1 / Page 2] sent American diplomat Richard Rush to England in 1836 to secure the bequest. After several years of legal proceedings, the British Court of Chancery finalized the inheritance transfer in 1838. Following years of congressional debate, President James K. Polk signed "An Act to Establish the Smithsonian Institution, for the increase and diffusion of knowledge among men" on August 10, 1846.

First Secretary of the Smithsonian Joseph Henry envisioned the institution as a center for original scientific research, particularly in the fields of physics, meteorology, and natural science. Its earliest collections reflected that focus as it began preserving plant and animal specimens. 

Construction of the Smithsonian Institution Building, known as the Castle, began in 1847. Upon its completion in 1855, the building's Great Hall exhibited scientific instruments and natural history specimens. Following the highly successful 1876 Centennial Exposition in Philadelphia, Pennsylvania, many of the exhibits were transferred to the Smithsonian. Congress subsequently appropriated funds for a new museum building to house the institution's growing collections. Completed in 1881, the National Museum Building—later renamed the Arts and Industries Building—hosted President James A. Garfield's inaugural ball on March 4, 1881, before opening to the public later that year.

On March 2, 1889, President Grover Cleveland signed legislation creating the National Zoological Park—commonly known today as the National Zoo—to house the Smithsonian's live animal collections, including American bison, elk, deer, prairie dogs, and beavers. In the decades that followed, the Smithsonian expanded to include museums exhibiting its vast collections of art and artifacts and scientific specimens, including the Freer Gallery of Art (1923), the National Museum of American History (1964), the National Air and Space Museum (1976), the National Postal Museum (1993), the National Museum of the American Indian (2004), and the National Museum of African American History and Culture (2016). Two additional museums are currently in development—the National Museum of the American Latino and the American Women's History Museum.

Today, the Smithsonian Institution continues to fulfill its founding mission to “increase and diffuse knowledge” through its museums, research centers, and educational programs. From its origins in a single act of Congress and the bequest of James Smithson, it has grown into a vast network dedicated to preserving history, advancing scientific understanding, and sharing knowledge with the public.

You can learn more about the Smithsonian Institution using Census Bureau data, for example:

• The Smithsonian Institution is nicknamed the "Nation's Attic." It houses approximately 157 million objects, but fewer than 1 percent are on display at any given time. Many of these items are stored and conserved at facilities near the Census Bureau's headquarters in Suitland, Maryland. Among them are the National Museum of Natural History's Museum Support Center, the Paul E. Garber Preservation, Restoration, and Storage Facility, the National Museum of the American Indian Cultural Resources Center, and the Smithsonian Gardens Greenhouse Facility.
• The Smithsonian Institution operates dozens of research centers and libraries around the world, such as the Smithsonian Astrophysical Observatory in Cambridge, Massachusetts; the Smithsonian Conservation Biology Institute in Front Royal, Virginia; the Smithsonian Environmental Research Center in Edgewater, Maryland; the Smithsonian Tropical Research Institute in Gamboa, Panama; the Smithsonian Marine Station at Fort Pierce, Florida; and the Smithsonian Museum Conservation Institute in Suitland, Maryland.
• The Smithsonian Institution Building, known as the Castle, was the first structure built to house the museum's collections. Construction began in 1847 and was completed in 1855. The building's exterior was made of red sandstone quarried in Montgomery County, Maryland. In 1850, there were 1,144 stone and marble quarries in the United States, including 35 in Maryland. Nationwide, these establishments employed 10,001 "hands." The total value of products produced by these quarries was nearly $8.2 million.
• A number of prominent special agents, geographers, scientists, and ethnographers made significant contributions to both the Census Bureau and the Smithsonian.
  • Cyrus Guernsey Pringle was an American botanist who spent his career studying and cataloging the plants of North America. He collected hundreds of thousands of plant specimens during his lifetime, some of which are in the Smithsonian's National Museum of Natural History collections. In 1884, the forest data he collected as a census agent were published in the Census Bureau's Report on the Forests of North America.
  • Ethnographer James Mooney worked for the Smithsonian's Bureau of American Ethnology from 1885 to 1921, studying American Indians, particularly the Cherokee, Kiowa, and Plains tribes. Between 1890 and 1910, he served as a census consultant assisting with data collection in American Indian communities.
  • Thomas Corwin Donaldson collected mineral samples and prepared an illustrated catalog of the Smithsonian's Indian Gallery in 1886. He also acquired Americana and artifacts related to the institution's benefactor James Smithson. In 1890, he was the chief of Indian Statistics for the Census Bureau and published several reports, including Six Nations of New York, North American Indians in the United States (Alaska excepted), Moqui Pueblo Indians of Arizona, Pueblo Indians of Mexico, and Report on Indians Taxed and Not Taxed in the United States (Except Alaska).
  • Henry Gannett served as geographer for the 1880, 1890, and 1900 Censuses as well as the censuses of the Philippines, Cuba, and Puerto Rico. He was instrumental in publishing the 1880 and 1890 editions of the Statistical Atlas of the United States. As chief geographer of the U.S. Geological Survey and co-founder of the National Geographic Society and the Association of American Geographers, he worked closely with the Smithsonian on mapping, surveying, geographic projects, and the standardization of geographic names and terminology.
  • In addition to early paper valentines, Dorothy Gale's Ruby Slippers from the 1939 movie The Wizard of Oz, and the Woolworth's lunch counter from the 1960 Greensboro Sit-Ins, the Smithsonian also houses many significant census-related artifacts. Some examples include 1860 Census tally sticks used to count the Nokoni Comanche Indians in Texas and New Mexico; a mechanical tabulator invented by Census Bureau employee Herman Hollerith; the serial plate from the Census Bureau's UNIVAC I computer; punch cards used to process census data; and sorting and tabulating machines built by Census Bureau technicians. 
• In 1860, the Census Bureau's headquarters was located in the Patent Office Building at 7th and F Streets NW in Washington, DC. Today, the Census Bureau is headquartered in Suitland, Maryland, while the historic Patent Office Building is home to the Smithsonian's National Portrait Gallery. Among the gallery's collections are portraits of Secretary of State Thomas Jefferson, who oversaw the 1790 Census; Secretary of State John Marshall, who oversaw the 1800 Census; and Superintendent of the Census Francis Amasa Walker, who directed the 1870 and 1880 Censuses.
• The Smithsonian Institution has hosted several exhibits about the census coinciding with the once-per-decade population census. In 1959, Census Bureau Director Robert W. Burgess worked closely with the Smithsonian on The United States Census 1790–1960 Exhibit. In 2020, the Smithsonian launched the U.S. Census: Counting on You online exhibit featuring artifacts such as a creamware jug displaying 1790 Census data, a 1900 Census enumerator's badge, 1930 tabulator punch cards, and advertising posters from 2000.

Article 1, Section 2, of the U.S. Constitution mandates that the United States conduct a count of its population every 10 years to apportion the number of representatives each state will have in the U.S. House of Representatives.

On March 1, 1790, President George Washington signed legislation into law—the 1790 Census Act (Page 1 / Page 2)—assigning U.S. marshals the task of conducting the nation's first census.

Marshals and their assistants traveled throughout the 13 states, as well as the districts of Kentucky and Maine and the Southwest Territory (present-day Tennessee), using rudimentary forms to record the name of each head of household along with a numeric count of each household's free White males age 16 and older, free White males under 16, free White females, all other free people, and slaves as of the first Monday of August 1790.

At its conclusion, the 1790 Census found that 3,929,214 people lived in the United States. The largest urban places were New York City, NY (33,131); Philadelphia, PA (28,522); Boston, MA (18,320); Charleston, SC (16,359), and Baltimore, MD (13,503).