Boggy,I'm thinking the practice of referring to areas as "Roberts Prarie"-to use an example from Jack County- was confined to that part of Texas along what is now the I-35 corridor and West to the confluence of the Clear and Salt Forks of the Brazos at present day South Bend Tx.
It stands to reason that the early settlers coming from the East would have been impressed by the large expanse of grassland.Once they moved further West,they discovered that the whole damned place could be called a "prarie",and I don't encounter many "prarie" place names West of Ft Griffin,for example.
Also, the praries in the Cross Timbers were short grass praries,unlike the country to the West which had the tall grass.They were also open range at that time.
In fact,I think it's likely that the "Salt Grass Prarie" rendered in the Army's reports probably should have been "Short Grass Prarie".It makes more sense.There are no local references to either term , as far as I know.
I think you've got the prairies turned around. I can't speak for Texas for sure, but up here, the farther west you go the more you get into the short grass. Where I live was considered Tallgrass, unless I'm mistaken. An educated guess would put the Cross Timbers as a pretty good boundary between the two probably being mixed country. I can't imagine there being much difference between here and there. As to the Salt Grass, I always thought that referred to the "piedmont-ish" areas close to the coast.
