Northeastern Maranhao is on Brazil's coastal plain. Southwestern Maranhao and Tocantins are on the nation's Central Highlands. On the southern border of Maranhao, the Chapado (Upland of) Penitente separates the two states, though these rise no higher than 1000 meters.
The most important northerly river, the Paranaíba, bounds Maranhao on the southeast. Much of that state's northwestern border is delimited by the Gurupi, while a piece of the western border follows the Tocantins(3). That river crosses the center of the state named after it from south to north. In southwestern Tocantins the branches of that river form a giant inland island, Bananal. A tributary of the Tocantins, the Araguaia, forms the western boundary of the more southerly state.
In common with Brazil generally
São Luis(4), Maranhao's capital, situated on the island with the same name between two bays, has just under a million residents, and a metropolitan area just over that threshhold. It is infamous as a slave port and famous for its bull dance festival, the 'Bumba-Meu-Boi.'
The only major language groups(5) from the area still extent are the Macro-Ge(6) and Tupi, specifically Tupi-Guarani.
Speculation about local Tupi languages
north
southeast of Maranhao
southwest of Tocantins
northwest
(1) Officially Brasil since the late 19th century.
(2) Nordeste in Portuguese.
(3) The Pará-Tocantins together constitute South America's sixth or seventh longest river.
(4) Translates as Saint Louis or Lewis from Portuguese.
(5) Joseph Greenberg would classify all pre-Columbian Brazilian language groups together as Amerindian.
(6) Sometimes considered part of a Ge-Pano-Carib group.