Between 1907 and 1909 an expedition led by Cândido Rondon crossed this region laying telegraph line, part of the vast project of wiring Brazil's interior to its coast. Rondon was a soldier and explorer of indigenous descent whose commission operated under one of the more remarkable orders ever given to armed men working in contested territory: die if you must, but never kill. The lines he strung and the routes he surveyed opened a path into land that had been, from the coastal republic's point of view, blank. In 1918 the surveyor and deputy Otávio Pitaluga proposed renaming the settlement of Rio Vermelho in his honour. Rondon lived to see a city carry his name; the state of Rondônia was named for him too.

Before Rondon there was the Vermelho — the red river — and the people who lived along it. The Bororo occupied this stretch of the upper Paraguay watershed long before any of it appeared on a Brazilian map, and their presence shaped the late-19th-century occupation as much as the military post at Ponte de Pedra, garrisoned between 1875 and 1890. Then came prospectors, hunting gold and gemstones with the usual mixed results. The first families arrived to settle in 1902. In August 1915 the state government formalized things by allocating 2,000 hectares for the town's development, and Rondonópolis became a municipality in its own right on 10 December 1953. It sits at 227 meters, low for the Mato Grosso plateau, with the Vermelho running through the south of the seat.

Prospectors did eventually find something worth the trip, but it was in the soil rather than under it. Soybeans transformed this part of Mato Grosso so completely that locals describe the boom in the language of the old gold rushes, and the migration patterns bear the comparison out: families arrived from the South and Southeast, many of them cattle people trading pasture for row crops. Farming here is extensive and heavily automated, on a scale that dwarfs most of Brazilian agriculture. Industry followed the grain — crushing plants, fertilizer handling, trucking — and the population followed the industry. A settlement that only became a municipality in 1953 now approaches a quarter of a million residents.

For decades the fundamental problem of Mato Grosso agriculture was distance. Grain grown here had to travel by truck down BR-163 to ports more than a thousand kilometers away, and freight cost eroded the advantage that cheap land and good yields provided. The rail terminal that opened at Rondonópolis in 2013 changed that arithmetic. It is the largest grain rail terminal in Latin America; at harvest peak it can load something on the order of 80,000 tonnes of soybeans in a day — the equivalent of filling a Panamax ship, every day, from a yard in central Brazil. The tracks currently end here, which is exactly why the city matters. Everything grown to the north still comes down by road to meet them.

It would be easy to picture Rondonópolis as nothing but flat cropland, and wrong. The city sits on cerrado tableland cut by deep gorges, with buttes and mesas standing out of the plain in bands of red rock. The 6,422-hectare Dom Osório Stoffel State Park, created in 2002, protects a piece of that landscape along the northern edge of the municipal seat. The climate is tropical savanna — summer afternoons pushing 35°C, winters merely warm. Travellers use the city as a staging point for the northern Pantanal, the great seasonal wetland that begins west of here and depends on rivers like the Vermelho and the Cuiabá to fill it. Maestro Marinho Franco Municipal Airport handles domestic flights; most visitors still come by bus down the highway.