Yea, the oldest continuously operating inland boat marina in all of Texas (located in deep E.Tx, since 1909 is....... ?

Johnson Ranch

I'd second that.

Johnson Ranch, Uncertain, Texas

Tell the story of the cabin on stilts in the cypress stand across from Johnson Ranch marina...

Too long a story for Bop to get into.
However, county line between Harrison County and Marion County runs through the water between Johnson Ranch Marina and the shack on stilts (still sitting right there since the 1930's).

The shack served catfish and beer for boaters passing by or coming over from Johnson Ranch (Johnson Ranch only 200 yards away in Harrison County which was a dry, no-beer county in the 1930's, 40's & 50's).
For folks without ah boat there was a popular row boat shuttle service from Johnson Ranch to the shack and back.
Can't remember the business name of the shack but am sure it can be found somewhere on the Internet (or from archives of the Harrison Historical Society).