Tutuila is, by far, the largest of the seven islands of the territory of American Samoa. All addresses on Tutuila, as on all other islands in the group, are zip code 96799, or Pago Pago, AS 96799.
Let’s be very clear about the size of Tutuila. Although 95% of the territory population is on Tutuila, that number is no more than 60,000 (census data is unreliable). The CIA factbook says there is150 miles of road in American Samoa (all islands) but this seems like a huge overstatement. There is maybe 60 miles of paved road (probably an over-estimate) on Tutuila. There are fewer than 10 “STOP” signs (depending on how many are actually standing) and no traffic lights. The absolute maximum speed limit is 30mph, although most areas have posted speed limits of 25mph or less. There are no cities, not even a large town on Tutuila or anyplace in American Samoa.