Piauí has the shortest coastline of any of the non-landlocked Brazilian states at 66 km (41 mi), and the capital, Teresina, is the only state capital in the north east to be located inland. The reason for this is, unlike the rest of the area, Piauí was first colonised inland and slowly expanded towards the ocean, rather than the other way around.
In the Southeast of the State is the National Park of Serra da Capivara is a UNESCO World Heritage Site. The park has more than 400 archaeological sites and the largest concentration of rupestrian (rock) paintings on the planet, in a landscape dominated by canyons and caatinga.
The first settlers in Piauí were bandits fleeing from São Paulo, notably Domingos Afonso Mafrense and Domingos Jorge Velho. Mafrense founded what is today Oeiras, whilst the first herds of cattle were taken there by Velho.
In the 1600s, many impoverished noblemen and Jesuit priests, as well as black and Amerindian slaves, settled there. The first large-scale cattle farming also arrived with these settlers. Large estate owners seeking new pastures for their livestock arrived from neighbouring states such as Bahia and Maranhão.
At the beginning of the 20th century, the principal industry of the state was stock-raising, which dates from the first settlement in 1674 by Domingos Affonso Mafrense, who established here a large number of cattle ranges. A secondary industry was the raising of goats, which were able to stand neglect and a scanty food supply. The agricultural products were cotton, sugar and tobacco. Forest products included rubber, carnauba wax and dyewoods. The exports included hides, skins, rubber, wax, tobacco and cotton.
Teresina was the first Brazilian city to be planned. In 1852, an architect designed it, after being inspired by a chessboard. Situated at the mouth of the Parnaíba and Poti Rivers, Teresina was (and still is) known as the Green City because of the countless mango trees that line the city's streets.
The Parnaíba River forms the boundary with Maranhão throughout its entire length, the state lies almost entirely within the basin of the Parnaíba and its tributaries. Part of the state on the Atlantic coast and along the lower Parnaíba is low, swampy, and historically malarial. South of this the country rises gradually to a high plateau with open campos. This plateau region is watered by numerous tributaries of the Parnaíba, chief of which are, from south to north: The Poti, which has its source in the state of Ceará; the Longa; the Canindé and its tributary the Piauí; the Gurguéia and its tributary the Parahim, which drains the large inland lake of Parnagua; and the Uruçui-Preto. The Parnaíba is navigable for boats of 1 meter draft up to Nova York, a few miles above the mouth of the Gurguéia. The river valleys are separated by flat-topped plateaus called chapadas, including the Serra Uruçui, which lies between the Uruçui-Preto and the Gurguéia, the Serra da Capivara, which lies between the Gurguéia and the Piauí, and the Chapada das Mangabeiras, which forms the southwestern boundary of the state, separating the upper basin of the Parnaíba from that of the Tocantins.
The sandy soils along the Atlantic coast are home to the Northeastern Brazil restingas, low evergreen forests adapted to the nutrient-poor conditions. The lower basin of the Parnaíba is home to the Maranhão Babaçu forests, which extend westward into Maranhão. This ecoregion dominated by stands of the Babaçu palm. The eastern portion of the state is dominated by the dry Caatingas shrublands, which extend across much of northeastern Brazil. The Cerrado savannas extend across the southwestern portion of the state, in the basins of the upper Parnaíba and Gurguéia rivers. Enclaves of Atlantic dry forests lie in basin of the Gurguéia, forming a transition between the Cerrado and Caatinga.
Serra da Capivara National Park is located in the Caatinga of the south-central part of the state, and protects numerous caves with ancient cave paintings.
According to the IBGE of 2007, there were 3,041,000 people residing in the state. The population density was 12.1 inh./km².
The last PNAD (National Research for Sample of Domiciles) census revealed the following numbers: 2,101,000 Pardo (Brown) people (69.1%), 760,000 White people (25.0%), 173,000 Black people (5.7%), 6,000 Asian or Amerindian people (0.2%).
Festa Junina was introduced to Northeastern Brazil by the Portuguese for whom St John's day (also celebrated as Midsummer Day in several European countries), on the 24th of June, is one of the oldest and most popular celebrations of the year. Differently, of course, from what happens on the European Midsummer Day, the festivities in Brazil do not take place during the summer solstice but during the tropical winter solstice. The festivities traditionally begin after the 12th of June, on the eve of St Anthony's day, and last until the 29th, which is Saint Peter's day. During these fifteen days, there are bonfires, fireworks, and folk dancing in the streets (step names are in French, which shows the mutual influences between court life and peasant culture in the 17th, 18th, and 19th-century Europe). Once exclusively a rural festivsl, today in Brazil it is largely a city festival during which people joyfully and theatrically mimic peasant stereotypes and clichés in a spirit of joked and good times. Typical refreshments and dishes are served. It should be noted that, like during Carnival, these festivities involve costume-wearing (in this case, peasant costumes), dancing, heavy drinking, and visual spectacles (fireworks display and folk dancing). Like what happens on Midsummer and St John's Day in Europe, bonfires are a central part of these festivities in Brazil.