on September 19, 1906. Beginning her college career in the 1920s, Mathias originally had planned to study mathematics, but she instead studied botany, getting her bachelor's, master's degree and PhD at Washington University in St. Louis by the age of 22.

She married Gerald Hassler, a PhD in physics, in Philadelphia in August 1930. From 1932 to 1936, Mathias was a research associate at the New York Botanical Garden and then at