Anna Gillette was born in Fountain City, Buffalo, Wisconsin, United States on 5 August 1890, the middle child of nine children born to parents John Koschitz (1848–1908) and Louise Erhardt (1860–1940). Her father ran the Eagle Brewery, which was next to the family’s home. She attended a Catholic school until the eighth grade before she began working at a sewing factory, where she sewed women’s bras. At night, she performed in an orchestra, where she played piano alongside four other musicians. In the 1940s, during World War II, she worked in an ammunition factory.

In July 1910, she married Claude Gillette, a railroad telegraph operator. Due to her husband’s job, they had free fare and were able to travel all across the United States. The couple later settled in Oquawka, Illinois, where Anna would reside for more than 50 years before returning to her hometown at the age of 90. She lived alone in her own apartment until she was 108, by which point she moved into a nursing home.

She passed away in Fountain City, Buffalo, Wisconsin, United States on 21 November 2001, at the age of 111 years, 108 days.