Moisés Santiago Bertoni was born in 1857 in Lottigna, in the Italian-speaking Swiss canton of Ticino, and studied at the universities of Geneva and Zurich. In 1884 he sailed for South America with his family and a band of fellow idealists, intent on building a colony around anarcho-socialist ideals. By the 1890s he had settled deep in the jungle on the banks of the Paraná River, at a spot still called Puerto Bertoni, and there he became one of the most relentless scientists the continent has known. He studied botany, meteorology, zoology, geography, and the cultures and languages of the Guaraní, much of his work done hand in hand with the indigenous communities who taught him their plants and their medicine.

Bertoni's name endures in the things he was the first to describe. Researching in eastern Paraguay in 1899, he became the first scientist to formally document Stevia rebaudiana, the unassuming herb whose leaves are reputed to be hundreds of times sweeter than sugar and which now sweetens products around the world. He also classified yerba mate, Ilex paraguariensis, the plant behind South America's beloved caffeinated drink. Yet recognition did not bring comfort. Bertoni died in 1929 at Foz do Iguaçu, on the Brazilian side of the great river he had made his home, an old man of seventy-two who passed away poor despite a lifetime of discovery.

The town that carries his name sits about 260 kilometers from Asunción, in green, rain-fed country where the land tilts gently toward the Paraná. Low hills of red sandstone give way to marshy esteros thick with palms, drained by the Ypety and Tebicuary rivers and their smaller branches. People here raise cattle and tend plantations of citrus, sugar cane, and eucalyptus, and along the Tebicuarymi River some still fish, both for their own tables and for market in the departmental capital. The river beaches fill in summer, and the old train station downtown remains a point of pride. Each February the district holds a jineteada, a feast of horsemanship, and in October it honors Saint Teresa with races, music, and a festival that draws performers from near and far.

The town began as a creature of the railway. Founded around 1880 as Estación Sosa, it grew at a stop on the line that once stitched together the towns between Caazapá and Yuty, the kind of place that lived by the rhythm of arriving and departing trains. The decision to rename it after Bertoni came in 1931, by Decree Nº 40.843 signed by President José P. Guggiari, and it placed the village within a long Paraguayan tradition of European settlers reshaping the eastern forests, from anarchist idealists to the German-speaking colonists who founded settlements elsewhere in the country. Bertoni was a different kind of immigrant, a scientist rather than a colonist, and the honor reflected how thoroughly Paraguay had claimed him as its own. Today, lodges like the Estancia Loma Linda invite visitors to ride horses and rest among the hills, and the station that gave the town its first name still stands as its quiet center.