The Tremembé were here first, along this whole stretch of shifting sand and brackish channel. Colonial administration arrived in 1758, when the settlement was raised to the status of a vila and given the tidy Portuguese name Vila Viçosa — a rebranding that failed, since the older name simply outlasted it. In 1901 the seat moved to Porto Salinas. The municipality in its present form dates from 29 March 1938. Three names, three centuries, one location that kept being renamed by people who had come to it recently and would not be the last word on it.

Where the name comes from is genuinely unsettled. The most colourful theory credits Phoenician traders in search of saltpetre, deriving Tutóia from a supposed "Turtoia" — a claim that tells you a great deal about nineteenth-century Brazilian romanticism and rather little about the town. The likelier explanations are indigenous. In Tremembé, the name is read as "sheet of sand" or "great expanse of dunes," which describes the ground exactly. In Tupi-Guarani it is glossed as "good water." And there is a fourth reading, from "Totói," translated as an exclamation: what beauty. Take your pick. The competing etymologies happen to name the three things the place actually consists of — sand, fresh water and a view worth an exclamation.

Tutóia is the second-largest coconut producer in Maranhão and ninth in cashew, on a municipal economy that reached about 414 million reais in 2019. Agriculture is only a fraction of that figure on paper, but it structures the place: at the 2010 census roughly two-thirds of the population lived in rural areas, at a density of about 34 people per square kilometre. The rhythm is set by the climate, which is generous and predictable — rain from January through June, dry from July through December, average temperatures above 27 degrees Celsius, and 1,200 to 1,600 millimetres of rain a year. The town itself sits about twenty metres above the sea, high enough to be dry and low enough to be part of the water.

East of town the coast dissolves. The Parnaíba, which forms the border between Maranhão and Piauí for its entire 1,400-kilometre run down from the Chapada das Mangabeiras, breaks into five arms and scatters into a maze of islands, channels, mangrove and dune before reaching the Atlantic. Tutóia is one of the gateways into that maze, and the whole municipality lies within the Delta do Parnaíba Environmental Protection Area, created by federal decree on 28 August 1996 across 313,800 hectares and ten municipalities in three states. The protected habitats are a checklist of northeastern Brazil's transition zones: coastal caatinga, restinga, mangrove and flood plains full of carnaúba palms. Past the last street the municipality stops being a shoreline and becomes an archipelago — bays, tidal flats that empty twice a day, and islands by the dozen.

Several buses a day run east to Parnaíba, a three-hour trip, the last one leaving at four in the afternoon. One a day goes west to São Luís. For Paulino Neves and the road to the dunes, the transport is a 4x4 pickup, an hour and a half, departing mostly to meet the buses coming in from Parnaíba — with one dependable run at ten in the morning. There used to be a scheduled boat across to Parnaíba, which would have been the more sensible way to travel; it is gone, though a motor launch can be chartered for up to four people. Accommodation is a handful of simple pousadas and a campsite outside town. There is, as the guidebook puts it with admirable honesty, a beach of sorts within walking distance.