Genevieve Stump Foster was born April 13th 1893 in Oswego, New York, but was fated to live the greater part of her childhood in Wisconsin following a family tragedy. Her father John William Stump, a science teacher, died only a year after she was born, and her mother Jessie Starin Stump moved herself and Genevieve to Whitewater, Wisconsin to live with her parents. Foster remembered a four-story brick house with a picket fence, kept by the family for four generations. As one of the greatest influences she noted in her development, it gave her a sense in her early years of the “continuity of past and present.” Another formative presence in Foster’s life was her grandmother whom she described as a “lively little old lady full of fun and always ready to play games,” and who taught her to sew and embroider when she was very young. Foster appreciated her grandmother’s example as influential; observing her sewing and lace making techniques taught her to finish a piece of work properly before starting another. The household faced other tragedies: her grandfather died when she was three years old, and the immediate family included an invalid aunt, a widow who spent large amounts of time in her room “with a fascinating green bottle of smelling salts beside her.” Nonetheless, as an only child she never remembered being lonely; the winter that she was five, her aunt was sick for weeks and Foster wrote her letters, pushing them under the bedroom door. Although no one made a particular effort to teach her, Foster learned to read and write. She also learned to draw, following a history of painting, drawing and modeling in the family. When she started school at age six, the house and yard afterwards were always full of children, and Foster had a studio on the top floor with two of her friends one summer where she also attempted to write her only novel at age ten, “of which Chapter One was both the end and the beginning.” By age thirteen Foster’s drawing teacher recommended to her mother that she attend art school immediately upon completing high school. However, she first attended Rockford College from 1911 to 1912 and went on to graduate from the University of Wisconsin in 1915 with a full classical course in a B.A. Eager to attend art school, as she had had no time to draw in college, Foster enrolled after graduation at the Chicago Academy of Fine Arts, which she attended from 1916 to 1917.

Her drawings caught the attention of the school’s director, who encouraged her to work in commercial art. She began by working freelance from a studio in the Fine Arts Building, and had a career as a commercial artist, illustrator, and advertiser. A series of booklet, magazine, and newspaper illustration work followed for several years, beginning with assignments for Mother's Magazine, Golfers, Extension, and Women's World. Foster didn't want to specialize in illustration and turned to advertising because it allowed her variety in work and ideas. Her work proved interesting, but was nonetheless never quite satisfying, and she gave up all but one account when she married the engineer Orrington C. Foster on June 5th, 1922. Their first five months of marriage were spent in the remote northern woods, and upon returning to Chicago, Foster drew upon her illustrator’s background to make blueprint drawings for a studio apartment building that she designed with her husband and built as their first home. She directed construction with her husband's help and also decorated and furnished their home. With the birth of her two children, Orrington C. Jr., known as Tony, in 1924 and Joanna in 1928, Foster centered her attention on her household for the next few years, also taking an active role in the Parent-Teacher's Association when they were in lower grades. Once the children were past infancy she returned to illustrating for children's stories during the depression from 1930 to 1938, which again proved fun but not completely satisfying. Even so, Foster worked as an illustrator and advertiser for Child Life magazine in 1931 and produced illustrations for Frances Cavanaugh's Children of the White House and Boyhood Adventures of the Presidents of 1936 and Clara M. Judson's Pioneer Girl, the Early Life of Frances Willard of 1939. The family moved to Evanston, Illinois in 1933.

Foster liked school and, while interested in all subjects, ironically had her greatest difficulties with history, which remained increasingly confusing through high school and college. She described her experience with the discipline as her mind being “stored with a conglomeration of events, dates, personalities and trivia, as ill assorted and distressing as the contents of an old-fashioned attic." This difficulty helped to motivate Foster to her final publication success; she came to the conclusion that she should combine all her favorite pastimes and find out what she had always wanted to know about history in the process, writing a history book for children as well as adults. Foster credits her daughter with the inspiration that crystallized her creative method. When she and Joanna saw the film Catherine the Great, her daughter noticed that Catherine wore clothes similar to people in America during the time of George Washington. This observation led Foster to her mode of writing about history in a "horizontal" instead of "vertical" fashion. She stated plainly that "history is drama," that national histories taught in isolation from one another were "about as dull and unsatisfying, as a play might be, if only one character appeared upon the stage, while the others faintly mumbled their lines in the wings, out of sight of the audience." Foster pioneered a new method of historical writing that turned on a cross-section of history, understanding the interconnections between various events.

The second crucial element of her method came from her observation that we remember and evaluate world events in correspondence to the events of our own lives. She theorized that a history book might use a similar method by gathering the events connected to the lifespan of a particular noteworthy figure and integrate the historical contexts in that time period on a global scale. Detailed indexing would allow readers to similarly follow other particular figures in the book over the course of their histories. Charles Scribner’s and Sons published her first “horizontal history,” George Washington’s World, in 1941 while Joanna was in the seventh grade and Tony in high school. Focusing on the span of George Washington's life from 1732 to 1799 allowed Foster to focus on the French and American Revolutions and the beginnings of British imperialism, as well as the interconnectedness of these events. The book was a huge success; Scribner’s considered it one of their "three most unusual" children's books and it was widely read by both children and adults.

Her next book published in 1944, Abraham Lincoln’s World, allowed her to continue in the progression of American history since Lincoln was born only nine years after Washington’s death. The popular World series written for middle-graders was followed by Initial Biographies for younger readers and the Year books, full of illustrations for readers in lower grades, for a grand total of nineteen children’s books over the course of her career. Foster described the overall project as "setting to rights a long neglected attic," by which she hoped to provide children with a history more comprehensible than that with which she had struggled. Foster’s husband Orrington died in 1945, the year after the publication of her second book and also that in which Tony graduated from Cornell University. Her next book, Augustus Caesar's World: A Story of Ideas and Events from B.C. 44 to 14 A.D., came out in 1947 while Joanna was enrolled at Vassar College. Foster expanded her history project to a greater scope in considering the evolution of Western beliefs around such events as the development of Christianity. Joanna was herself inspired to follow in her mother’s footsteps, beginning as an assistant children’s editor in the Juvenile department of Scribner’s from 1950 to 1952 and eventually publishing two children's books of her own: Pete's Puddle with Houghton in 1950, and Dogs Working for People with the National Geographic Society in 1972. Foster later used her method to write a new kind of travel book, When and Where in Italy , published by Rand McNally in 1955, that gave similar historical backgrounds for visitors to this country. Her family grew over this period to include three grandchildren: John Starbuck Foster and Genevieve Dougherty in 1961, and Catherine Starin Foster in 1963.

Foster traveled extensively in Europe, Asia, and the Pacific Rim, and her books proved to be widely popular. Most were translated into over twelve foreign languages and distributed by the State Department. Several were nominated as Newbery Honor books: George Washington's World, Abraham Lincoln's World, George Washington, and Birthdays of Freedom Book I. Additionally, George Washington won the Boys' Clubs of America 1950 Award. Her books had a similarly impressive impact in the educational field; George Washington's World, Abraham Lincoln's World, and Augustus Caesar's World were all used as basic history texts in a number of schools, and George Washington's World gained particular notoriety when it was used for one semester by the tutor educating the Crown Prince of Japan. Foster held memberships in Midland Authors, and the Theta Sigma Phi journalism and Gamma Phi Beta sororities over the course of her life. She passed away September 17th, 1979 in Westport, Connecticut.