Growing up, the girls moved with their family to Chicago's West Side before they started school. They were in all the same classes, each wearing a sign with their first initial pinned on with a ribbon so their teachers and classmates would be able to tell them apart.
As they got older, they ditched the signs and Primack wore a red ribbon around her wrist. They always dressed alike in clothes their mother sewed for them.
"By 17, we minded," Eisgrou said of their matching outfits.
After graduating in 1927, they both went to work, their parents unable to afford college. Eisgrou worked as a saleslady at Sears for years while Primack did office billing for a company that made jewelry.
Eisgrou moved to Florida in 1949 with her second husband -- her high school sweetheart died after less than three years of marriage -- and the twins were forced to learn how to live apart.
Then, in 1971, Primack followed to Florida with her husband. The couples visited reguarly with their children and took long trips together.
Both of their husbands are now deceased -- Primack's husband lived to be 92 -- and while the women don't see each other as often as they'd like anymore, they talk by phone at least every other day.
"They are a trip," said Jerry Primack, who flew in from California for two of the twins' birthday parties. "They're so cute. They're just cute."
Though not as active as they once were, they both say they are staying busy. Eisgrou attends card games and excerise class in her condo building. And Primack goes out shopping with her caregiver and watches movies on television and in the theater when her son visits.
Both women say they are often asked how they managed to make it to 100.
"Everybody asks me that. I don't know what it was," Primack said. "I didn't watch my food when I was young. I smoked. We all smoked."
Eisgrou said her secret is milk, which she has drunk every single day of her life. Her sister, though, teases her for telling people that.
"I always felt that. She always laughed at me," Eisgrou said. "But it was always milk."