William Hartman McFadden (June 11, 1869 – November 1, 1956) was an American businessman and an essential factor in opening up the oil fields of Oklahoma.

At age 19 he apprenticed in the Mackintosh Hemphill Steel Foundry in Pittsburgh, Pennsylvania, and in 1909, at the age of 40, he became president of Mackintosh Hemphill, but resigned shortly thereafter due to ill health, suffering from lungs irritated by a galvanizing compound used in steel mills.

In 1910 he was approached by John G. McCaskey, a social acquaintance from Pittsburgh, and E. W. Marland, president and founder of the 101 Ranch Oil Company of Ponca City, Oklahoma, that was on the verge of failure, having run out of money after drilling seven wells and only having found natural gas.

(1) McFadden was impressed with Marland and, after visiting the Miller Brothers 101 Ranch property, decided to invest in the company.

Shortly thereafter a drilling lease was obtained on the Willie Cry Ponca Indian allotment, and on June 11, 1911, the well “Willy-Cries-For-War” struck oil, bringing wealth to the company and its investors.