This structure is known as the Old Stone Fort. As best as I can guess, it was likely an outpost of Fort Riley, which is about a day's ride away by horse. The site overlooks an important stream crossing and cattle trail which were vital in driving cattle to the railroad, about another five miles away. The buildings don't look like a ranch. There is a stable, but not a barn so there was no provision for large quantities of livestock feed nor crop storage. Besides, only the Army would put the livestock stable upwind of the living quarters.