Marguerite Garde was born in New York City on 23 March 1909, the oldest of three children born to parents Anna W. and Charles Christian Ruess. Growing up in the Bronx during the Great Depression, she had to work as a young teenager in order to support her family. She trained to be a secretary in Manhattan, and later worked in radio at the Rockefeller Center during the lead-up to World War II.

She married Edward Garde in New York City in 1942. Shortly thereafter, Edward would enlist in the army, and was sent overseas. After the end of World War II, the couple were reunited, and moved to the state of New Jersey, where they raised their two children. Her hobbies including knitting, crocheting, baking, gardening, and reading. After her children were grown, she would later return to her career as a legal secretary, continuing in this field until retirement.

Following the death of her husband in 1986, Garde moved to St. Francis Residential Community in Denville, New Jersey, where she resided before later moving into a retirement home in Parsippany, New Jersey at the age of 103. She stayed healthy and active well into her centenarian years, continuing her exercise of taking long walks until she was 107.

She passed away on 29 July 2019, at the age of 110 years, 128 days.