From the record
“The Rio Grande Ranch Headquarters Historic District is a historic one-story residence located 3 miles (4.8 km) east of Okay in Wagoner County, Oklahoma. The site was listed on the National Register of Historic Places September 9, 1992.”
Wikipedia article Rio Grande Ranch Headquarters Historic District, CC BY-SA 4.0.
One of 19 National Register listings published here for Wagoner County · listed in 1992 · category: District.
Sources: the Wikipedia article · the case file at the National Archives · the National Register database, National Park Service