Ernestina A. López was born in January 1879 in Buenos Aires, Argentina to Cándido and Adriana W. López. She began her teaching career and became Director of the Sarmiento Model School. In 1890, she founded the Liceo Nacional de Señoritas and thereafter served as its rector. In 1901, she earned the first doctorate degree issued to a woman in letters and philosophy from the University of Buenos Aires and in 1902 joined 31 other women including Petrona Eyle, Cecilia Grierson, , her sister Elvira López, Anna Pintos, and Elvira Rawson de Dellepiane to form the Argentine Association of University Women ( (AMUA), as a means of addressing employment biases against women and female university graduates. The group actively worked to attain legal, civic and educational rights for women. In 1904 López attended the St. Louis World's Fair exposition as Argentina's delegate for the National Council of Education.