Your USPTO: Finding Lost X Patents

Find out how you can help recover the archives of America’s first innovations

In December 1836, a catastrophic fire at the United States Patent Office destroyed the records of American innovation preserved from the earliest days of the Republic. We call the patents from this era (1790-1836) “X patents” – not because they are shrouded in mystery (although they are), but because they predate the numbering system currently in use.

Adam Bisno, the USPTO’s official historian, writes that X patents were registered by inventor’s name and date of issue. It was not until after the fire of 1836, as the Patent Office was rebuilding its collection, that examiners began to retroactively number early grants.

To distinguish them from contemporary patents, numbered from 1 (issued July 1836) to 11 million (issued May 2021) and counting, the letter X was affixed.

Eli Whitney’s patent for the cotton gin, for example, issued in 1794, became 72X. This was separate from U.S. Patent No. 72, issued in October 1836 to Silas Lamson for an improvement in the construction of scythes. We now refer to all patents prior to U.S. Patent No. 1 (issued July 13, 1836) as X patents.

The fire of 1836 destroyed the specifications and models of nearly 10,000 X patents. The only remaining documents were kept by the inventors themselves, in the form of “letters patent”, manuscript precursors to typewritten digitized today.

Standing amid the ashes, Commissioner of Patents Henry L. Ellsworth faced an impossible situation. With the transition to a rigorous examination system, enacted just five months before the fire, the Patent Office now relied on records of past inventions to determine the patentability of future inventions.

To continue to function – to survive – the Patent Office needed these documents, and fast.

The solution became the Patent Office’s first attempt to crowdsource its own story. Within months, Congress and Commissioner Ellsworth issued a call to patentees for information about their inventions. Based on the replies sent by post, some 2,800 patents could be reconstructed. But the others – more than 7,000 – have never been found.

Chronically overworked, late 19th century patent examiners had little time to search for missing Patent Office documents.

In the 20th century, the fire of 1836 and the lost documents have become a distant memory for all but a few patent history buffs. These volunteers — archivists, librarians, historians, patent examiners, and interested members of the public — have found hundreds of patent Xs, and the USPTO is adding the scans to its Patent Full-Text and Image Database (PatFT) for several years. . The work continues to this day, with X patents now also available on the USPTO’s public patent search site.

The surviving X patents are scattered far and wide. Some are in large repositories like the National Archives and the Smithsonian Institution. Others are in national and local archives, buried among the papers of inventors, their companies or their families.

If you find one that is not already listed in the USPTO’s public patent search, please notify the USPTO Historian ([email protected]), and we’ll add it to the database.

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