William Maclure (1763–1840), geologist and educational reformer, was a native of Ayr, Scotland, who received a classical education by private tutors before entering commerce. After visiting the United States on business in 1782, in London he joined the firm of Miller, Hart & Company, for which he traveled extensively in Europe and America and through which he amassed a fortune. Maclure moved to Philadelphia in 1796, retired from business the next year, became a naturalized citizen, and turned his attention to science. He befriended TJ by 1798 and was elected to the American Philosophical Society in 1799. In the latter year Maclure moved back to Europe, where he conducted extensive geological studies. He returned to the United States in 1808 and made a geological survey of the eastern states. The pioneering geological map in his “Observations on the Geology of the United States” (APS description begins American Philosophical Society description ends , Transactions 6 [1809]: 411–28), which he revised and issued separately under the same title (Philadelphia, 1817; Poor, Jefferson’s Library description begins Nathaniel P. Poor, Catalogue. President Jefferson’s Library, 1829 description ends , 5 [no. 173]; TJ’s copy in MiU-C), helped establish Maclure as the leading American geologist. After traveling throughout Europe between 1809 and 1816, he returned to Philadelphia and became the key patron of its Academy of Natural Sciences, of which he was president from 1817 until his death. Maclure was also named the first president of the American Geological Society in 1819. Back in Europe from 1818 until 1825, he helped promote the Pestalozzian method of teaching. His efforts to establish an agricultural school in Spain were thwarted by political turmoil there. In 1824 Maclure met Robert Owen in Scotland and became involved in the latter’s New Harmony community in Indiana, where Maclure helped to establish a center for scientific research. He moved to Mexico in 1828 for health reasons, but he maintained an active correspondence with the scientific community and founded the New Harmony Working Men’s Institute Library in 1838. Maclure died in San Ángel, Mexico (ANB description begins John A. Garraty and Mark C. Carnes, eds., American National Biography, 1999, 24 vols. description ends ; DAB description begins Allen Johnson and Dumas Malone, eds., Dictionary of American Biography, 1928–36, 20 vols. description ends ; DSB description begins Charles C. Gillispie, ed., Dictionary of Scientific Biography, 1970–80, 16 vols. description ends ; John S. Doskey, ed., The European Journals of William Maclure [1988], xv–xlviii; APS description begins American Philosophical Society description ends , Minutes, 19 July 1799 [MS in PPAmP]; PTJ description begins Julian P. Boyd, Charles T. Cullen, John Catanzariti, Barbara B. Oberg, and others, eds., The Papers of Thomas Jefferson, 1950– , 41 vols. description ends , 33:341–2, 34:503–4; American Journal of Science, and Arts 2 [1820]: 139–41; Maclure, Opinions on Various Subjects, dedicated to the Industrious Producers, 3 vols. [1831–38]; Philadelphia Public Ledger, 29 Apr. 1840).