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.