Near Valhalla KS?
Valhalla KS is or was in Gove county, 2 counties over from the Colorado border. I did not find it listed on map of KS Ghost towns. "Jerome (Gove County) Post Office 1886-1943 – Little remains of the townsite." Nearby Alanthus is listed as a Ghost town. The Town of Ransom still exists....
As they note: "The roads to Castle Rock are unpaved and may be impassible in wet weather."