Pengra was the eldest of five children born to Wisconsin farmer and landlord Winfield Sherman Pengra and Mary Ellen (Preston). All five of the couple's children went on to earn a University of Wisconsin bachelor's degree in nearby
Madison. Charlotte received her Bachelor of Arts degree in mathematics from the university in 1897, which, like the degrees of most female graduates of that time, qualified her to teach math at secondary schools. For two years she taught at Wisconsin high schools in
Fox Lake and
Sparta. After winning a fellowship in 1899, she was able to return to the University of Wisconsin-Madison to advance her studies there. She earned her doctorate two years later, in 1901, under the direction of Linnaeus Wayland Dowling. Her 23-page doctoral thesis, about the conformal representation of plane curves, was titled
On Functions Connected with Special Riemann Surfaces, In Particular Those For Which P Equals 3, 4, and 5. After receiving her doctorate, Pengra moved to
Elgin, Illinois where, for three years, she served as supervisor of a high school mathematics department. The first of their three children, a daughter, was born November 1906 in Germany and the other two children were born in 1909 and 1911 after the family's return to the U.S. The young family settled in Illinois where Arthur took a faculty position at the
University of Illinois.
Charlotte Pengra Crathorne died in 1916 of breast cancer in
Brodhead, Wisconsin at the age of 40. == Publications ==