Local government officials believe it spread from neighboring Samoa, where an outbreak closed schools for a week last month.
The territory's Department of Health issued a health alert on pink eye last week after the number of cases spiked at community health clinics and a hospital.
Dr. Joseph Tufa, the department's medical director, said on territory-run public television Thursday night that total numbers were not yet available.
Parents and government officials say that the number of cases will be higher than what's reported because many people are opting to stay home rather than go to a doctor.
The territory's largest private school system, the Office of Catholic Education Service, closed Friday and was expected to remain shuttered Monday. The closure encompasses a high school, three elementary schools and two kindergartens, with more than 700 total students enrolled. Other smaller private schools were also closed.
"The pink eye epidemic is moving quickly, affecting several of our students and teachers," said Eddie Brown, the Catholic school system's director.
The outbreak also affected court cases, with most criminal hearings in the High Court of American Samoa postponed Thursday and Friday because the assistant public defender was out sick with pink eye.
Marshals were screening those entering the building for pink eye, with about four people turned away from court Friday.
Several District Court cases were also postponed.