Molly Pitcher's real name was Mary Ludwig, the daughter of German settler, John Georg Ludwig, a butcher in Philadelphia. She was born on October 13, 1744, and was raised to be a hard worker. In 1768, Mary Ludwig was hired by a Mrs. Irvine from Carlisle, Pennsylvania, who wanted a young girl to help with the housework. Mary Ludwig lived with Doctor and Mrs. Irvine for some years, and it was there that she met her husband, William Hays. They married on July 24, 1769.

In 1775, the Revolutionary War began, and Hays enlisted in May, 1777, in the Colonial Army in Briston, Bucks County. Mary Ludwig Hays followed her husband to war, a custom in the British Army and, to some extent, among the American troops. Following her husband's regiment, she nursed the sick and assisted in cooking and washing. On June 28, 1778, in Freehold, New Jersey, during the Battle of Monmouth, Mary Ludwig Hays earned the nickname "Molly Pitcher," becoming one of the most popular female images of the Revolutionary War. On that day, during the Battle of Monmouth, Molly Pitcher performed an act of unusual heroism, an act that would go down in history as legendary. That day in Freehold, New Jersey, it was told that Mary trudged back and forth from a nearby spring bringing water to the soldiers on that hot and smoky battlefield. Welcoming the sight of the sparkling water, the weary soldiers nicknamed her "Molly Pitcher." According to some accounts, on one of her trips from the spring, Molly Pitcher, as she was always called thereafter, saw her husband collapsing next to his cannon, unable to fight. Molly dropped her pitcher and took over his position, and she was seen firing the cannon throughout the dreadful battle until victory was achieved. Her act of heroism on that day earned her a sergeant's commission, given by General Greene, some even say by George Washington himself. An old Revolutionary rhyme tells the story:

Moll Pitcher she stood by her gun And rammed the charges home, sir; And thus on Monmouth bloody field A sergeant did become, sir.

There is a famous painting named Molly Pitcher and the Battle of Monmouth, painted by Dennis Malone Carte, which depicts this heroic deed. It was painted in 1854, and it is currently displayed in the Fraunces Tavern Museum in New York.

Until the close of the Revolutionary War, Molly Pitcher remained with the army and proved to be a beloved and valuable helping hand. Following the death of her husband, she lived at the Carlisle barracks, cooking and washing for the soldiers for many years. After William Hays's death, she remarried a war veteran named John McCauley. They settled in Carlisle, where Mary went back to work as a domestic in the State House in Carlisle. Mary Ludwig Hays McCauley was known familiarly in Carlisle, Pennsylvania, where she lived for the rest of her life, as Molly Pitcher. She lived on the corner of North and Bedford streets in a house which since has been demolished.

In 1822, the legislature of Pennsylvania awarded Molly Pitcher a sum of forty dollars and an annual commission of the same amount during her lifetime. On January 22, 1852, Mary Ludwig Hays McCauley died in Carlisle, Pennsylvania, and was buried in the old Carlisle cemetery with military honors—a company of soldiers firing a salute. On the Fourth of July, 1876, the 100th anniversary of the Declaration of Independence, the citizens of Carlisle erected a white marble monument inscribed to "Molly Pitcher, the heroine of Monmouth," over her grave. A poem by Laura E. Richards commemorating Molly can also be found on her grave. Molly Pitcher was a typical American woman during her time period, but her bravery and her dedication for the Country is nothing but exceptional. Mary Ludwig Hays McCauley, or simply Molly Pitcher, was a true heroine, and a true valiant American soldier.

The legend of Molly Pitcher has been told for many generations. Her stories have inspired many women of her time and captured the hearts of America. In 1928, Molly Pitcher was honored with an overprint reading "MOLLY / PITCHER" on a U.S. postage stamp. Molly was further honored in World War II with the naming of the Liberty ship SS Molly Pitcher, launched in 1943. It was used to encourage the use of the ration program and the purchase of treasury bonds during World War II. The stretch of US Route 11 between Shippensburg and Chambersburg, Pennsylvania is known as the Molly Pitcher Highway.