History of the Expedition under the Command of Captains Lewis and Clark, Vol. I. : To the Sources of the Missouri, Thence Across the Rocky Mountains and Down the River Columbia to the Pacific Ocean. : Performed During the Years 1804-5-6.

William Clark (died 1603) was an English Roman Catholic priest and conspirator. He is remembered for his involvement in a plan to kidnap King James I of England, made together with another Catholic priest William Watson in the Bye Plot. He was executed at Winchester on 29 November 1603. He wrote A Replie unto a certain Libell latelie set foorth by Fa. Parsons, in the name of the united Priests, intituled, A Manifestation of the great folly and bad spirit of certaine in England calling themselves Secular Priestes, 1603, no place.