X Patents are some of the earliest patents issued by the United States government. Unfortunately, many of these early patents and corresponding models were destroyed in the Great Fire of 1836, while in temporary storage during a period when a new storage facility was being built. Prior to the fire, the United States had issued about 10,000 patents; however, most of the destroyed patents will never be recovered.
Immediately after the fire, Congress quickly acted to restore the patents that could be reconstructed. Many of these reconstructions were the result of the inventor’s own copy or private records. If the record of a patent could not be restored, they were canceled.
Those patents that were able to be restored were given a new series number being with an “X.” The very first of these “X” patents was issued to Samuel Hopkins in 1790 for his invention for an improvement in the making of pot ash bearing the number X000001 shown below.