Margaret Sidney was the pen name of Harriet M. Stone. She was born in Connecticut in 1844. After publishing Five Little Peppers and How They Grew in the magazine Wide Awake, Margaret married the publisher, Daniel Lothrop. Together they bought Nathaniel Hawthorne_s home, The Wayside, in Concord, Massachusetts, where Margaret wrote, raised their children and pursued philanthropic interests. She died there in 1924.
For more information, check out http://www.library.ufl.edu/spec/manuscript/guides/Sidney.htm.