Margaret Mercer was born in 1791 as the daughter of Governor John Mercer of Maryland. She few to be a highly educated, independent woman as well as a renowned and outspoken opponent to slavery.
When her father died in 1821, Margaret educated and freed her family's slaves. In 1836, Margaret relocated to Loudoun County and purchased Belmont Manor which she converted to the Belmont Academy. The Belmont Academy was a girls' school well known for its quality curriculum and high standards.
Margaret was endowed with an inquiring mind as she pursued the subjects of theology, medical science and agriculture which, at the time, was deemed unsuitable for women.
A controversional abolitionist, Miss Mercer ignored legal constraints and continued to educate slaves within Loudoun County. She was quite vocal and a prolific writer regarding slavery which she deemed "the most peculiar institution
Miss Mercer died of tuberculosis in 1846 and was buried at her beloved Belmont Chapel. Her monument at Belmont reflects the love from her students and is inscribed with the following:
Sacred to the memory of Margaret Mercer, Born July 1, 1791, Died September 17, 1846. Her remains repose beneath the chancel of this chapel built by her own self-denying labors. This monument is erected by her pupils as a testimony of their admiration of her elevated Christian character, and of their gratitude for her invaluable instructions.