The patents

The number in widest circulation is “over 700”, and it usually arrives with nothing attached: no jurisdiction, no date range, no reference. It is printed that way by organisations that present themselves as authorities on the subject. The smallest published figure, 112, comes with a list you can read line by line.

Both can be arrived at honestly, because a patent is granted in one country at a time. An inventor who wants protection in a dozen countries files a dozen applications for a single invention. Count national grants and you get one figure; count inventions and you get a much smaller one; count both without saying which you are doing, and almost any total can be produced.

The Nikola Tesla Museum in Belgrade, which holds his papers, publishes the list of United States grants. It runs to 112. It begins with US 334,823, a commutator for dynamo-electric machines granted on 26 January 1886, and ends with US 1,655,114, an apparatus for aerial transportation granted on 3 January 1928 — forty-two years apart. Published analyses that add filings elsewhere identify roughly 199 further patents across some two dozen other countries, protecting on the order of 125 inventions once duplicate national filings of the same thing are collapsed together. No route through those figures reaches 700.

What a granted patent is evidence of.

It means an examiner accepted that the claims, as drafted, were new and useful. It does not mean the thing was built, or worked, or sold. Some of the documents below describe machines that were built, did work, and reorganised an industry inside a decade. Others describe arrangements that were never realised at any scale. The list is a record of claims, not of achievements, and reading it as a scoreboard is exactly the habit that produces the 700.

Filing dates and grant dates are not the same date.

Two dates matter and they are constantly conflated. US 1,119,732 was filed on 18 January 1902, renewed on 4 May 1907 and granted on 1 December 1914 — nearly thirteen years from the original application, a period during which the Wardenclyffe property was mortgaged twice. A renewal date is not a filing date, and printing it as one is the commonest error in lists of these patents. Priority runs from the filing date, which is why accounts of the rotating-field patents say “1887” and “1888” interchangeably and are both right. Where one application was split into several, the divided case keeps the parent's filing date: US 382,280 carries 12 October 1887, although the divisional papers were filed on 9 March 1888.

What this table is, and what it is not.

Nineteen United States grants, transcribed one at a time from the patent faces: number, title exactly as printed, filing date, grant date. They are the documents the articles on this site are built on, together with the first and last US grants, which fix the two ends of the record. This is a subset of the 112, not the whole list. A row appears only where the face was read directly; where the scan could not be read cleanly, the row was left out rather than filled in from a secondary compilation. The museum's own published list is the reference for the remainder.

A note on the group column.

The groups are this publication's, not the Patent Office's. They are a reading aid: Early work for the arc-lighting and dynamo patents of the mid-1880s, Polyphase for the rotating-field machines of 1888, High frequency for the oscillator and coil work of the 1890s, Wireless for the transmission scheme that led to Shoreham, Signalling for the tuning and control patents, and Mechanical for the turbine, pump, valve and aircraft work after 1909. The Patent Office classified these differently and its classifications changed several times in the intervening century.