I can't find patent citations on patents from 1836. Was there a specific date or year that citations were added to patents?

  • The "duty of candor" regarding prior art was not codified until 1977, with enactment of 37 CFR 1.97, the "prior art statement". Whether that led immediately to inclusion of the cited lists in the issued patents would require more research. Patents cited by US examiners have appeared in patents since as early as the 1950s.
    – Upnorth
    Commented Aug 21, 2017 at 5:29
  • That is an interesting history question. I looked up US patents number 1,000,000, 2,000,000 and 3,000,000. The first two, filed in 1910 and 1932, respectively, don't cite any references; the third one, filed in 1955, does. If you find a definitive answer, please post it.
    – Riccati
    Commented Aug 30, 2017 at 20:14


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