Simplify the following text for a Grade 5 native English-speaking person.
Original: It is not uncommon for people to mistakenly refer to Mato Grosso do Sul as simply `` Mato Grosso '' .
Simplified: Mato Grosso do Sul was a part of Mato Grosso until they were split in the 1970s . Many people wrongly refer to Mato Grosso do Sul as simply `` Mato Grosso '' .