In 1895, at 60 years old, Fields was hired as a mail carrier because she was the fastest applicant to hitch a team of six horses. This made her the second woman and first African American woman to work for the U.S. Postal Service. She never missed a day, and her reliability earned her the nickname “Stagecoach Mary.” If the snow was too deep for her horses, Fields delivered the mail on snowshoes carrying the sacks on her shoulders.
Mary is said to have had a penchant for whiskey, cheap cigars, and brawling. It was not uncommon for men to harass her because of her race or her gender. Big mistake. The six foot tall, two-hundred pounder was only too happy to serve up a knuckle sandwich. Until her death at the age of 82, she had a standing bet at her local saloon: Five bucks and a glass of whiskey said she could knock out any cowboy in Cascade, Montana, with a single punch. According to her obituary in Great Falls Examiner “she broke more noses than any other woman in Central Montana.”
In 1959, actor and Montana native Gary Cooper wrote an article for Ebony in which he said: “Born a slave somewhere in Tennessee, Mary lived to become one of the freest souls ever to draw a breath, or a .38.”