She earned a Bachelor of Arts degree from Goucher College in 1908, and a master's degree in mathematics from Columbia University the following year. After teaching at Wisconsin, she decided to study civil engineering and studied at Cornell University. In 1920, she became only the second woman to obtain a Civil Engineering degree from Cornell. She was hired that year as a draftsman by the B & O Railroad to design bridges. The following year, the President of the railroad observed that, since half of the railway's passengers were women, the task of engineering upgrades in Service would best be handled by a female Engineer. Dennis became the first "service engineer" when the B. & O. created the position. Engineering Historian Kurt H. Debus described her as the first Service Engineer in America. She was also the first female member of the American Railway Engineering Association.