Catherine McAuley was a devout Irish woman who lived in the 1800s. She was deeply committed to her faith and prayed every day. Catherine felt a heavy heart seeing so many young women without a place to call home and children without adequate clothing, shoes, or food. She was also concerned about young women who could not find work and children who could not afford to attend school.

When Catherine inherited a sum of money, she knew precisely what she wanted to do with it. She built a large house in Dublin's Baggot Street and named it the House of Mercy. The House of Mercy became a bustling hub, attracting other women who shared Catherine's passion for helping others. Together, they embarked on several activities to help those in need. They cared for parentless children and young women without homes, set up a school for underprivileged children, and attended to the sick and dying. 

Catherine strategically chose Baggot Street as the location for the House of Mercy because it was an area where wealthy people lived. She believed that by doing so, the rich people would become more aware of the struggles of the poor in Dublin. By watching Catherine and her team of helpers provide warm shelter, food, and education to the needy, some wealthy families also wanted to contribute. They offered financial support and provided job opportunities to poor women who could earn their own income.

Catherine was convinced that this was her divine purpose.

Catherine and her helpers became the Sisters of Mercy. To distinguish themselves, they wore long black gowns and hats. They pledged to God that they would assist the sick and impoverished in their area and provide education for children and young women. Unlike other nuns who mainly stayed in convents, the Sisters of Mercy were called the "walking Sisters" because they actively served the community.

Today there are still many Sisters of Mercy worldwide helping people.