While supplying pitchers of water to feed the fighting Continental soldiers on the field of battle, she saw her artilleryman husband fall wounded. She subsequently picked up the rammer and "manned" the cannon, making her the second woman to fight on the American battlefield (Margaret Corbin in 1776 being the first).
After the battle, General George Washington issued her a warrant as a noncommissioned officer, and she was thereafter known by the nickname "Sergeant Molly".
In 1928, she was honored with an overprint reading "MOLLY / PITCHER" on a US postage stamp.