Alexander Deussen, petroleum geologist, was born on January 19, 1882, in San Antonio, the son of Charles and Clotilda (Nordhaus) Deussen. Though his parents were natives of San Antonio, where his father was vice president at the Groos National Bank, his grandparents were of German and English descent. In his youth Deussen attended the German-English Grammar School, which gave instruction in both English and German. He then attended San Antonio High School before going on to the University of Texas at Austin, where he received his bachelor's degree in 1903 and master's degree in 1904. After receiving his M.A., Deussen took a position teaching geology at the University of Texas; he stayed there ten years. On August 23, 1905, he married Sue Burnett Campbell. Deussen had met her as a student in one of his classes, and she affectionately referred to her husband as "the Professor." Later in life they divided their time between their Houston home and their ranch, Deussendale, located on Elm Creek in northeastern Texas. They had one daughter. While teaching at the University of Texas, Deussen also held the position of assistant geologist in the United States Geological Survey from 1907 to 1915. At the end of this appointment he began work for the Guffey Petroleum Company, which would later be renamed Gulf Oil Corporation. In 1916 Deussen resigned his position with Guffey to work as an independent consulting geologist. Except for a brief interlude between 1924 and 1930, when Deussen served as vice president in charge of operations for the Gulf Coast Region for Marland Oil Company, he remained devoted to his private consulting practice for most of his life.
Deussen's study of the Gulf Coastal Plain is perhaps his most noteworthy contribution to the field of geology. In 1924 he directed the first seismographic survey of the Gulf. That year he was also instrumental in establishing one of the earliest laboratories devoted to the research and study of Gulf Coast sediments. His study, "Geology of the Coastal Plain of Texas West of the Brazos River" (first published by the United States Geological Survey in 1924 and again in 1930 by the University of Texas), is one of his more ambitious scholarly investigations into this area. Previously, in 1921, Deussen had discovered an oil well in the Mexia district, which was the first of the fault-controlled fields in East Texas (see WOODBINE FAULT-LINE FIELDS). His vanguard work in this area was a great contribution to the oil industry in Texas. Deussen was an active member in the American Association of Petroleum Geologists, serving as its second president in 1918–19. In 1947 he was awarded the Sidney Powers Memorial Medal by the American Association of Petroleum Geologists for his contributions to the field of petroleum geology. He was also director of the American Petroleum Institute from 1923 to 1925 and a member of a number of societies, including Phi Beta Kappa and Sigma Xi. Deussen was a Democrat and a Presbyterian. In 1954 he donated a 200-acre site on Lake Houston to Harris County. The site was converted into a public park and named the Alexander Deussen Park. Alexander Deussen died on September 5, 1959, in Flow Hospital in Denton, near Ponder, Texas, the site of his ranch home.