Which was the last South American country to become independent?

The last South American country to become independent was Ecuador, which declared its independence from Spain in 1822.

The last South American country to become independent is Suriname. To confirm this, we can follow these steps:

1. Start by identifying the major South American countries that gained independence from their European colonial powers.
- Brazil: gained independence from Portugal in 1822.
- Argentina: declared independence from Spain in 1816 along with other territories that formed the United Provinces of the Rio de la Plata.
- Colombia, Venezuela, Ecuador, and Bolivia: were part of the Gran Colombia, which declared independence from Spain in 1819 but dissolved later on.
- Chile: declared independence from Spain in 1818.
- Peru: declared independence from Spain in 1821.
- Uruguay: gained independence from Brazil in 1828.

2. After examining this list, we can see that Suriname is missing.
- Suriname was a Dutch colony until it gained independence from the Netherlands on November 25, 1975.

Hence, Suriname is the last South American country to become independent.

The last South American country to become independent was Suriname.