The short answer? It was destroyed by a fire. However, that short answer doesn’t illustrate the true demise of the 1890 census.
In 1890, for the first time in the history of the census, there was a separate sheet for each family. A question regarding service during the American Civil War was asked, which included those that served as well as widows of soldiers. The census also asked how many children women had and how many were still living. The census, if it had survived, provided insight into immigration, industrialization, and westward expansion of the nearly 63 million people. According to the Library of Congress, nearly 12 million immigrants arrived in the United States between 1870 and 1900. Many of these people appeared for the first time in the 1890 census along with details regarding these families that are now lost to history. Historians and genealogists keenly feel the loss of this census when tracking the movements and lives of people between 1880 and 1900.
So, what happened?
The 1890 census seemed doomed from the start. In March 1896, the original 1890 special schedules for morality, crime, pauperism and benevolence, special classes, and portions of the transportation and insurance schedules were damaged by fire according to the National Archives. This ultimately led to their destruction by the Department of the Interior. There were no reports of the population schedules suffering any damage. In 1921, the schedules were in an unlocked room in the basement of the Commerce Building, despite requests for an archive building for the safety of the census schedule. On January 10 of that year, building fireman James Foster spotted smoke about 5 o’clock. When other firemen arrived, they began hosing water into the building and flooded the cellar. With no disaster or recovery plan of historic documents and artifacts at the time, the Chief Clerk opened the windows to let out smoke and everyone went home after the fire was extinguished.
The next day, water was still ankle deep in some areas covering records and while the vault was considered fireproof and water tight, water leaked in and damaged some earlier and later census records. However, the 1890 census was stacked outside the vault directly in the path of the fire and water. According to the Census Director at the time, Sam Rogers, an estimated 25% was destroyed with 50% damaged by water, smoke, and fire. No cause was ever discovered for the fire but speculation and rumors spread from a cigarette to spontaneous combustion.
At the end of the month, the damaged records moved to temporary quarters and it was recommended the remaining 1890 census schedules be destroyed. Many prominent people and organizations wrote in asking that the schedules not be destroyed and that an archive building be built. However, nothing was done for the damaged census and information regarding its movement is scarce until 1932. That year, the Chief Clerk of the Bureau of Census sent the Librarian of Congress a list of records deemed no longer necessary as part of the federal retention schedule. The Librarian did not identify any records as worthy of historical preservation which included the population schedules from 1890. Congress authorized their destruction on February 21, 1933.
The 1890 census schedules were thought to be completely gone until 1942, when surviving Illinois schedules were accessioned after being found during a Census Bureau move. In 1953, more fragments were accessioned from Alabama, Georgia, Illinois, Minnesota, New Jersey, New York, North Carolina, Ohio, South Dakota, Texas, and the District of Columbia. In total, only 6,160 names survived of the 1890 population schedules of the nearly 63 million person count.
 Ellis Island opened in 1892 and was America’s largest and most active immigration station until 1924.
Blake, Kellee. “’First in the Path of the Firemen’: The Fate of the 1890 Population Census, Part 1.” Prologue 28, no. 1 (Spring 1996). Accessed February 25, 2020. https://www.archives.gov/publications/prologue/1996/spring/1890-census-1.html.