Elementary Charge 1869-1959 Charles Thomson Rees Wilson [Wikipedia] 1856-1940 Joseph John Thomson [Wikipedia] 1874-1964 Harold Albert Wilson [Wikipedia] 1868-1953 Robert Andrews Millikan [Wikipedia]
1899	Thomson He employed the technique of a cloud chamber developed by Charles Thomson Rees Wilson. e = 6.8x10-10 stat C = 2.27x10-19 C ( 1 stat C = 3.335641x10-10 C ) J. J. Thomson On the masses of the ions in gases at low pressures London, Edinburgh, and Dublin Philosophical Magazine Journal of Science 5th Series, Volume 48, pp. 547-567 (1899). [DOI] C. T. R. Wilson The effect of Röntgen's rays on cloudy condensation Proceedings of the Royal Society of London A, Volume 59, pp. 338-339 (1896). [DOI] C. T. R. Wilson Condensation of water vapour in the presence of dust-free air and other gases Proceedings of the Royal Society of London A, Volume 61, pp. 240-242 (1897). [DOI]
1903	H. A. Wilson He calculated the elementary charge from the velocity of the water droplet affected by the electric field. e = 3.1x10-10 stat C = 1.0x10-19 C H. A. Wilson A determination of the charge on the ions produced in air by Röntogen rays London, Edinburgh, and Dublin Philosophical Magazine Journal of Science 6th Series, Volume 5, pp. 429-441 (1903). [DOI]
1909	Millikan Modified water drop experiments. What's modified ? "This modification of the cloud method of determining e consists: 1. In making observations, not upon the surface of a cloud, but upon single isolated drops carrying multiple charges. 2. ... 3. ..." Results: 4.66x10-10 stat C = 1.55x10-19 C R. A. Millikan A new modification of the cloud method of measuring the elementary electrical charge, and the most probable value of that charge Physical Review Series I, Volume 29, pp. 560-561 (1909). (in Proceedings of the American Physical Society. Minutes of the Forty-Seventh Meeting) [DOI] [Caltech]
1910	Millikan Oil drop experiments e = 4.9016 x 10-10 statC = 1.635x10-19 C R. A. Millikan The isolation of an ion, a precision measurementof its charge, and the correction of stokes's law Science, Volume 32, pp. 436-448 (1910). [DOI]