Birthday cake was served to the zoo's gorillas and human visitors alike, zoo officials said.
Colo, short for Columbus, Ohio, got her name from a national "Name the Baby Gorilla" contest.
She gave birth three times in the late 1960s and early '70s. She has16 grandchildren, seven great-grandchildren and two great-great-grandchildren.
The Columbus Dispatch noted Colo weighed 3 pounds, 4 ounces when she was born to Christina, a 280-pound gorilla captured in the French Cameroons.
Ohio State University veterinary student Dean Thomas cut the umbilical cord and breathed into Colo's mouth to start respiration and quickly transferred her to a human incubator, the newspaper said.
Zoo Superintendent Earl F. Davis, said Colo's mother appeared afraid of the newborn and he credits Thomas with saving her life.