The boundary of the Anthropocene geological time interval as an epoch is evaluated. Of the three main levels suggested in the literature so far (i.e., an 'early Anthropocene' level some thousands of years ago; the beginning of the Industrial Revolution around 1800; and the 'Great Acceleration' of the mid-20th century), current evidence suggests that the last of these has the most pronounced and globally synchronous signal. We propose an appropriate boundary level here to be the time of the world's first nuclear bomb explosion, on July 16th 1945 at Alamogordo, New Mexico; additional bombs were detonated at the average rate of one every 9.6 days until 1988 with attendant worldwide fallout easily identifiable in the chemostratigraphic record. Hence, Anthropocene deposits would be those that may include the globally distributed primary artificial radionuclide signal, while also being recognized using a wide range of other stratigraphic criteria. This suggestion for the Holocene/Anthropocene boundary may ultimately be superseded, as the Anthropocene is only in its early phases, but it should remain practical and effective for use by at least the current generation of scientists.