"I feel like I did when I was 16," Ms Gries said on her birthday on Thursday. "I don't feel my age. I can't believe it."
Some things have changed in the 58 years she has been selling for Avon - she hires a driver for her twice-monthly rounds, and she does not see or hear as well as she used to.
Nonetheless, Ms Gries has vowed to sell Avon for "as long as I can walk". She has about 25 customers in the sparsely populated area of North Dakota where she lives.
Ms Gries has gained fame for her long service - even making a television appearance on The Tonight Show in 1986.
Avon paid tribute to its oldest salesperson by throwing a party for Ms Gries."Tomorrow starts a new day and then I have to start over again," she said.