The Tale of Peter Rabbit, which she illustrated herself, was published in 1902. It was an instant success and was followed by a series of books. I loved the Peter Rabbit books as a child and love even more reading them to my son (and him reading them to me).
You can get The Tale of Peter Rabbit as well as the Peter Rabbit collection if you don't already have them.
Thank you Beatrix Potter for writing Peter Rabbit and sharing it with the world. And…Happy Birthday!