The area beyond the coastal plain is part of Brazil's Central Highlands which reach their highest in northwest Ceará. The area is drained by short rivers like the Jaquaribe, flowing directly to the Atlantic.
In common with Brazil generally
The two state capitals have metropolitan areas exceeding one million people. Fortaleza, Ceará's capital, grew to its current size largely due to the Brazilian government making it the development center for the Northeast Region starting in the second half of the 20th century. Natal, the smaller capital of Rio Grande do Norte, offers sites from the old--a 16th century fort--to the new--the nearby rocket base of Barreira do Inferno.
All but one pre-Columbian linguistic group is gone so reconstructing the past from the present languages is not a useful approach, the more so since that one language is unclassified into a large group(6). So no more can be said than that the previous inhabitants all belonged to groups that Joseph Greenberg collectively calls Amerindian. Later Tupi became an important lingua franca along the coast.
The impact of the Portuguesenorth of both states, and east of Rio Grande do Norte
east of southern Ceará, and south of both states
west
(1) Officially Brasil since the late 19th century.
(2) Nordeste in Portuguese.
(3) Translates from Portuguese as Big River of the North.
(4) Translates from Portuguese as 'Ferdinand of'.
(5) São Pedro e São Paulo is their official Portuguese label.
(6) The only known extinct language from here is also unclassified.