Santa Maria is a municipality in the central region of Rio Grande do Sul, the southernmost state of Brazil. In 2020, its population was 283,677 …Santa Maria is a municipality in the central region of Rio Grande do Sul, the southernmost state of Brazil. In 2020, its population was 283,677 inhabitants in a total area of 1,823 square kilometres. Santa Maria is the 5th biggest municipality in the state, and the largest in its micro-region.