It all began in 1842 with the discovery of the 'Vau do Iguaçu' (literally meaning 'Iguazu Ford'), the best connection between the South and the Southeast Region, where the army troops and people from Rio Grande do Sul known as 'tropeiros' used to cross the river with their oxen in order to sell them in São Paulo and Minas Gerais.

It was also an important stop point for those who used the river in transportation, receiving its first name: Porto da União (Harbour of Union).

The small village grew and in 1855 its name was changed to Porto União da Vitória.

In the same year, immigration began with the influx of Germans, Poles, Ukrainians, Italians, Austrians and Russians.

Porto União has a subtropical Cfa-like climate with hot summers and rainy months