•Radiocarbon date of wooden stilts from 11 villages suggest phases of construction from ∼1st to 13th centuries A.D. (1912 ± 82 to 816 ± 88 calibrated years BP).•A radiocarbon date from one site suggests a much earlier habitation in the 4th millenium B.C (6622 ± 119 calibrated years BP).•The Formoso site has dates spanning the longest duration, ∼417 years (255–579 years).•Ceramic sherds and artifacts at Formoso suggest ceremonial activity and possibly foreign cultural influence.•The Formoso site has an uncommon village layout, possibly meant to resemble the Pleiades. Archaeological surveys conducted in the Maranhão estuaries of Brazil, near the Atlantic coast, revealed the remnants of 21 prehistoric stilt villages constructed on piles of Tabebuia handroanthrus hardwood above three seasonal flood water estuaries. Radiocarbon dates of 27 samples from 11 of those sites yielded an Archaic Period of construction (6622 ± 119 calibrated years before present) followed much later by consecutive construction periods from approximately the first century B.C. to the thirteenth century A.D. (1994 to 728 cal. yrs BP). The Formoso site—currently dated as the longest occupied site (1509 to 930 cal. yrs BP)—yielded early Incised-Punctate/Arauquinoid pottery, a previously unreported pottery style in the Amazon region. Additionally, using StarryNight astronomy software, the night sky at Formoso was compared with a map of the pile dwelling layout, revealing a statistically significant resemblance to the Pleiades. This paper focuses on the Formoso site, suggesting that it may have served cultural significance to the Pleiades as early evidence for the later widespread ethnographic use of the star cluster’s annual sighting to mark the seasonal flood cycles and the management of agricultural and ecological activities throughout tropical South America.