For the first 46 years after the Patent Act of 1790, the sitting US President personally signed every patent granted under their administration. Unfortunately, most patents bearing an original signature of a president were lost in the 1836 fire of the US Patent Office however two surviving patents are available to visit in person at the USPTO’s Public Search Facility. While modern day presidents no longer routinely sign patent grants, on special occasions they still may be. Most recently, President Trump signed the 10,000,000 patent to be granted in the US on June 19, 2019.
Source: The history of presidentially signed patents | USPTO