What languages did the siouan speak?

The term "Siouan" refers to a language family, not a single language. It's like saying "Indo-European" - it encompasses a wide range of languages.

The Siouan language family includes:

* Siouan proper: This branch includes languages like Lakota, Dakota, Nakota, Osage, Omaha, and Kansa. These are spoken primarily by indigenous groups in the Great Plains and the Midwest of the United States.

* Catawban: This branch is extinct, but was once spoken in the Southeastern United States.

* Tutelo: This branch is also extinct, but was once spoken in Virginia and North Carolina.

So, there isn't one "Siouan" language, but rather a diverse group of languages with varying degrees of mutual intelligibility.