The US Patents Office was nearly completely burned down.
All 9,957 patents and 7,000 patent models were lost in the blaze. It was initially suspected to have been an act of arson, but this was soon ruled out. The office shared a building with the post office, and careless disposal of ashes by the post office staff was deemed to be the source of the fire. After this, the US Patent Office changed its policies to require multiple copies of all patent documentation.