Bareville Fire Chief Nelson Oberholtzer says three other girls were transported to hospitals following the collision Thursday morning in West Earl Township, Lancaster County.
WGAL-TV reports the girl airlifted to Hershey Medical Center is 2 years old.
Officials at the scene say an elderly driver struck the open cart, which rolled several times. The driver told the Intelligencer Journal/Lancaster New Era that the cart appeared in front of him very suddenly.
The crash remains under investigation.