Heiligman was born in Allentown, Pennsylvania and lived in the same house her entire childhood. One of her favorite school memories is of her fourth grade teacher, Mrs. Ryan, who created magical reading nooks for her students — like an old clawfoot bath tub where Heiligman would climb in for a long read. She majored in religious studies as an undergraduate at Brown University, and in those classes discovered how to ask good, probing questions and to write with discipline, detail, and intent. Her writing career started kind of by accident — but a very happy accident - when she landed her first professional job as a writer for Scholastic New Explorer in New York City. At Scholastic she wrote about a wide range of subjects, everything from panda bears for first graders to pesticides for sixth graders. Heiligman loves the research process and says she is good at it because of her natural inquisitiveness (she calls it "being nosy"). Her freelance writing career began when she became a mom and wanted to balance a writing life with family life.

Heilgman has written more than 26 books, including the acclaimed Holidays Around the World series. Her fascination with the marriage of Charles and Emma Darwin led her on a great research adventure that brought her to the Galapagos Islands and the Darwin home in England as well as deep inside their diaries and letters. Heiligman is an active blogger on the I.N.K. (Interesting Nonfiction for Kids) blog and recently helped establish a companion site for teachers called INK Think Tank, whgich connects great nonfiction books with curriculum standards.