For over 100 years, female geologists have enjoyed careers in petroleum geology. They have been successful in finding oil and gas as employees, as managers, entrepreneurs, and as innovators in oil-finding technology. In the years closely succeeding their impactful work, their contributions were ignored, forgotten, or transferred to male colleagues.Five of the earliest women in industry remarkably illustrate the practice of minimizing or eliminating the records of their accomplishments. These are the stories of Alva Ellisor (1892-1964), Esther Applin neé Richards (1895-1972), and Hedwig Kniker (1891-1985) who revolutionized economic exploration for oil and gas worldwide with their discovery of the usefulness of foraminifera in biostratigraphy. Fanny Carter Edson (1887-1952) applied her unconventional background in hard rock mining geology to introduce the use of heavy minerals for correlations in difficult Paleozoic sandstones of the Midcontinent US. And, Dollie Radler Hall (1896-1995), the first female geologist manager in an oil company, pioneered the application of reflection seismic technology, and played a large role the in the discovery of the Williston Basin as an oil province. Defying the image of early women in petroleum geology being strictly “office” geologists, as they were often referred to, they were devoted to field work and visiting well sites when work demanded.Ellisor, Applin, Kniker and Radler Hall took advantage of the critical need for geologists during World War I (WW I) to gain or further their geologic education and used it to enter the world of petroleum as the war ended. Edson, who earned her degree in 1910, before WW I, became a mining geologist out of college but then turned to petroleum after WW I opened the career to women.