Mary Hickling, 39, of Lincoln Park died after the tree fell Saturday night at Hayes State Park in Cambridge Township, about 60 miles southwest of Detroit in Lenawee County.
Police said Hickling's husband and two children, ages 7 and 11, weren't injured.
Several campers rendered first aid and helped clear away tree debris. Hickling was pronounced dead Sunday at a hospital.
Hayes State Park Manager Jim O'Brien said the tree had "no signs of problems" before it fell. The state Department of Natural Resources is investigating the incident.