Rio Grande is a municipality and one of the oldest cities in the Brazilian state of Rio Grande do Sul. It was the state capital from 1835 to 1845. It is the most important port city in the state and has one of the most important maritime ports in Brazil.The city is named after a nearby channel which indirectly connects the Lagoa dos Patos, to the northeast, and Lagoa Mirim, to the west, with the Atlantic Ocean. The municipality is bordered by Santa Vitória do Palmar on the south and Pelotas on the north, which lies across the São Gonçalo Channel.The city built up its wealth over the course of its long history of strong industrial movements. Today it is still one of the richest cities in Rio Grande do Sul, mainly because of its port, the second busiest in Brazil, and its refinery, which processes Ipiranga petroleum.The city is served by Rio Grande Airport.HistoryThe history of Rio Grande is as old as the history of the whole region. It was explored by Portuguese sailors led by Martim Afonso de Sousa who sought fortified places along the southern Brazilian coast for a defense against the French corsairs. He discovered the tributary which indirectly connects the Lagoa dos Patos and Lagoa Mirim to the Atlantic Ocean and called the place Rio Grande de São Pedro (lit. "Large River of St. Peter").