McMillen was active in Provincetown, MA c. 1915. Known for working exclusively in black and white, she completed a woodcut titled, "Merry-Go- Round, Paris" in 1914. McMillen is included in "From Paris to Provincetown: Blanche Lazzell and the Color Woodcut" by Barbara Stern Shapiro.
During the summer of 1915, hundreds of Americans fleeing the advent of World War I, flocked to Provincetown, MA. The seaport came to be known as an artist’s colony. It was during this time that a group of artists, including Mildred McMillen, Ida Gilmore, Ethel Mars, J.O. Nordfelt, Maude Squire and Juliette Nichols came together to form the group known as the “Provincetown Print” (later they were known as the “Provincetown Printers”). They moved into houses and apartments near each other and worked solely on designing prints in the traditional Japanese manner.
The creative energy in Provincetown, along with the influence of Japanese woodblock print and the theories of Cubism and Abstract Expressionism led to the development of the Provincetown Print, a truly unique American art form.