Meinzer was born on a farm near Davis, Illinois, in 1876. He graduated magna cum laude from Beloit College in 1901 and received his Ph.D. in geology from the University of Chicago in 1922. He joined the USGS as an aide in 1906 and in 1912 succeeded W. C. Mendenhall as chief of the Division of Ground Water.
His long term as ground water chief, from 1912 to his retirement in 1946, often is referred to as "the Meinzer years." It was a period of rich intellectual achievement during which researchers developed the fundamental blocks of knowledge that would support the new science.
Oscar E. Meinzer is best known for his leadership at the U.S. Geological Survey (USGS). His career with the USGS spanned 40 years (1906–1946), when hydrogeology first gained recognition as a significant branch of earth science. Under Meinzer's leadership, a systematic scientific approach was applied to the problems of hydrogeology, and the underlying principles were defined. His work in codifying and organizing elements of the many disciplines related to the study of ground water helped define the fundamental concepts and underlying principles of a new science called ground water hydrology. His early involvement in studying the principles and occurrence of ground water in the United States earned him the moniker "father of modern ground water hydrology."
In 1923 Meinzer published two reports that formalized the status of ground water hydrology as a science and that provided a state-of-the-art review of the ground water field. In aggregate, these benchmark reports, "The Occurrence of Ground Water in the United States, with a Discussion of Principles" and "Outline of Ground Water Hydrology, with Definitions defined the breadth, scope, and philosophy of the new science. They provided a generation of ground water hydrologists with clear guidance and high standards for the conduct of ground water investigations.
In 1931 Meinzer was Chair of a Committee tasked with setting up a Section of Hydrology of the American Geophysical Union (with Robert Horton as vice-Chair).
Committee on Opportunities in the Hydrologic Sciences, 1991, Opportunities in the Hydrologic Sciences, Water Science and Technology Board, National Research Council, http://www.nap.edu/catalog/1543.html
R A Freeze, 1985, Historical Correspondence Between C. V. Theis and C. I. Lubin, EoS Trans. AGU v66(20), May 14.