Who controlled the Gran Chaco before the Chaco War?

[Alternate History]

I'm making a forum game and I decided I might as well be obsessed about every tiny detail. The game would be set before the Chaco War and I'm interested in how things were in the disputed Gran Chaco territory between Bolivia and Paraguay. Is there perhaps a map of who held what? Or did Bolivia pretty much control all of the disputed territory? (Which is one version I've seen, but other sources indicated that both of them were competing for it and had some presence.)

 

[Carl Schwamberger]

Can your game model local bandit gangs, and the strength of local ranch owners & their vaqueros?

 

[Alternate History]

Eh, well, in a rather abstract form maybe. I mean, it's not that it would focus exclusively on that region.