Mary Agnes Yerkes, who went by Agnes, was born on August 9, 1886 in Oak Park Illinois. She received an education from the School of the Art Institute of Chicago, Rockford College, and the Chicago Academy of Fine Arts. She married a Navy Commander, Archibald Nelson Offley, and lived in several ports in the early years of their marriage, eventually settling in San Mateo, California. Around this time the Great Depression began to take effect and she realized that she might not be able to further pursue her professional career as an artist. She continued to paint and took great inspiration from the American West and its National Parks. She passed away in 1989 at the age of 103.