According to the 2011 census Mier has a population of 7,003, which is the smallest of any municipality in South Africa. It is also the most sparsely populated municipality in the country, covering a land area of 22,468 square kilometres (8,675 sq mi) with a population density of 0.31 inhabitants per square kilometre (0.80/sq mi). Mier is the municipality in South Africa with the highest percentage of Afrikaans speakers at 97.1%.
The name Mier is an Afrikaans word that originates from the word "mere" which means "lakes". When German missionaries visited the area a long time ago, they found the pans in the area full of water. They called them "mere". As language changed, the people later pronounced it as "mier".