Where was the Sumerian language spoken in ancient Mesopotamia?

The Sumerian language was primarily spoken in the southernmost part of Mesopotamia, a region historically known as Sumer.12

This area, which later became Babylonia and corresponds to modern-day southern Iraq, extended from the vicinity of Baghdad down to the Persian Gulf. The language never extended significantly beyond these original geographic boundaries in southern Mesopotamia. Even as the Sumerian civilization flourished and influenced the broader region, the use of the language as a spoken tongue was eventually limited to Sumer proper before it was replaced by Semitic Akkadian around 2000 BCE.12