"Miss Annie", as she was called, was born in Baltimore on July 11, 1850, the second youngest of five children. Her Baptist roots and the religious climate of the late nineteenth century, helped Miss Annie to become a "shaper of missions." Miss Annie's  mother was a devout Baptist and active in her church and her father died when she was an infant. With her mother as a role model, Miss Annie's involvement in mission activities evolved through her home and church environments. 

The City of Baltimore also influenced Annie Armstrong. Living in the city broadened her horizons and facilitated her interest in the Black population, immigrants, the sick, and the poor. A turning point in Miss Annie's life came in 1880 after she heard a speech on the destitute conditions and needs of Native Americans in Oklahoma. She and other women organized to gather gifts of money and clothing. This experience crystallized her idea of encouraging women to organize into groups to educate and help the needy. Annie Armstrong founded and served as the first president of the Woman's Baptist Home Mission Society of Maryland (1882) and the Missionary Union. Until 1906, she concurrently held these two leadership positions while also supervising the Maryland Missions Room. Under her leadership, what started as a mission library and reading room, expanded to become a publisher and distributor of mission literature. She also served as an auxiliary to the Southern Baptist Convention of 1888.

With her ability to pull forces together, Miss Annie unified the mission efforts of all the Protestant denominations. She worked tirelessly for unity within the Southern Baptist community.

Beyond addressing a national meeting of the Woman's Auxiliary of the National (Black) Baptist Convention, she taught Bible classes, held mother's meetings, and prayed with the group. She encouraged other women's groups to interact similarly with Black people in their respective communities. As a result of this, two Black women were appointed as missionaries.

While working as a missionary with Native Americans, Miss Annie was able to provide needed clothing and supplements. She also rallied to support mountain people and immigrants who were arriving at the port of Baltimore. Annie Armstrong's mission work encompassed people of all cultures, races, ages, and economic levels. She was a "dreamer in action." When she saw a need, she dreamed about how to meet that need and was gifted in involving others to carry out that dream.

Miss Annie resigned her leadership positions in 1906 in opposition to the inclusion of the Women's Missionary Union training school with a men's seminary. She believed that the organization could not devote attention to missions and women's work in churches while raising funds to manage a school. After her resignation, Miss Annie continued her missions lifestyle. She immersed herself in church activities involving the needs of her city. One of her quotations still inspires us today, "The future lies all before us...shall it only be a slight advance upon what we usually do? Ought it not to be abound, a leap forward, to altitudes of endeavor and success undreamed of before?"

Annie Armstrong died on December 20, 1938.