Nancy Leek is a librarian who writes biographies of California pioneers for children. Her book on Peter Lassen, like her biographies of John and Annie Bidwell, are illustrated by Steve Ferchaud.
From GoldReads:
My name is Nancy Leek. I live in Chico, California and am a retired librarian. I have worked in public, school and academic libraries, including reference librarian for the Butte County Library and children’s librarian at the Orland Free Library.
I am the author of John Bidwell: The Adventurous Life of a California Pioneer, and the co-editor (with John Rudderow) of The Miner Poet: The Poems of Pres Longley.
In 2015 I started a series of picture book biographies for young readers called Golden State Biographies. So far the series includes John and Annie Bidwell: The Long and the Short of It and Nancy Kelsey Comes over the Mountain.

These books have full-color illustrations throughout by the talented Steve Ferchaud. They are colorful, exciting, and fun to read, and I have received enthusiastic feedback from California schoolchildren.
All books are available by contacting me at goldfieldsbooksca@gmail.com.