After school Marguerite visited the library. Her favorite books were biographies and mysteries. Reading Western adventures by Zane Grey, she decided that she wanted to own a ranch someday where she could see horses play. She knew that she would need money to be able to own such a farm, so she got a job at the library repairing books.
Marguerite still wanted to write, but in college, she decided to become an English teacher. One summer, she took a trip with her sisters to a fishing camp where she met her future husband, Sidney Henry.
When they were married, Marguerite kept writing articles for magazines. Her husband suggested that she try writing for The Saturday Evening Post. She submitted an article and it was published. She then wrote for popular magazines such as Reader’s Digest. Her husband traveled a lot, so Marguerite focused on her writing. After writing her first children’s book, Auno and Tauno, a story she heard from a friend about Finland, Marguerite decided to become a writer for children. This book is still available for sale online, after almost 70 years.
Marguerite later found the book, Flip, by Wesley Dennis and loved the illustrations. She decided to send him one of her books, Justin Morgan Had a Horse, to see if he would illustrate it. He agreed, and the book won a prize as a Newbery Honor Book.
In 1945, Marguerite received a letter telling the tale of ponies that washed into the sea hundreds of years ago when a Spanish galleon crashed on a hidden reef. The ponies swam for the nearest shore at Assateague Island.