Kate's Commonplace Book began as an assigned idea from one of the nuns who Kate was taught by. This was the first document of Kate Chopin's writing.

After the war, Kate almost had a depressed manner and one of the nuns of the Academy recognized the creativity in this lonely child. The nun assigned her to write a Commonplace Book, which is the first document of Kate's writings. This Commonplace Book became a diary of her intellectual and social life. She wrote on both sides of lined pages using black ink and she numbered the pages herself. The pages are now a brownish coloring, but are believed to have been white or cream colored. The back of the book is broken and many pages are loose, because so many researchers have read it in the past twenty years. Kate used many different types of handwriting in this book, including her flowery "schoolgirl" writing, her honeymoon tiny scripting, and her larger "flourishes" towards the end. There are many small spelling errors which could be because of Chopin's use of a dipping ink pen, so that mistakes have to be crossed out to be fixed.

At the age of 19, Kate met Louisiana native Oscar Chopin, a cotton broker, and married him on June 9, 1870. The last writings in her Commonplace Book are the diary of her 3-month European honeymoon. As was typical for a woman in her era, she doesn't mention sexual matters, yet she records the consummation of her marriage on June 12 in Philadelphia. The couple established their new home in New Orleans and awaits the birth of their first child, presumably conceived while honeymooning in France.

Cut off from the women of her family, who remained at home in St. Louis, Kate Chopin stopped writing in her Commonplace Book. She began her life as an adult woman, wife, and mother, in Louisiana. The Commonplace Book is now kept at the Missouri Historical Society.