Katherine Applegate was born in Michigan in 1956. Since then she has lived in Texas, Florida, California, Minnesota, Illinois, North Carolina, and after living in Pelago, Italy for a year, she has moved back to Southern California.
In 1997, she and her husband, Michael Grant, her co-author on many projects, including Animorphs and Everworld, had their first child, who has since come out as a transgender woman. In 2003, they adopted a daughter, Julia, from China.
Following the end of Animorphs, Applegate took three years off. She is back at work and her book "Home of the Brave" won the SCBWI Golden Kite Award, the Bank Street 2008 Josette Frank Award, and is a Judy Lopez Memorial Award honor book.