Martha was born in 1875 in the city of Philadelphia, Pennsylvania. As a youth she attended Girls High School in her hometown. She later continued her education at the Pennsylvania Academy of the Fine Arts under William Merritt Chase. During her time there she was also awarded the prestigious Charles Toppan Prize in 1902 and a Cresson Traveling Scholarship in 1903, which enabled her to visit Europe. She first attended the Academie de la Grande Chaumiere in Paris but, feeling restricted by the teachers' classical approach, enrolled instead in the Academie Julian. She eventually set up her own studio with a group of other young American women artists in Paris and learned the plein air techniques of the French Impressionists. In the time Walter was in France, she developed the characteristic style of bold, dashing brushstrokes. Her works grew more and more spontaneous, and color became of paramount importance. Cecilia Beaux said that Walter's beach scenes "seemed as if they were blown onto the canvas. Walter continued to paint until a few years before her death in 1976 at the age of 101.