San Calixto in the Wichita Mountains - the Sierra Jumanos - was probably the base for gold prospecting after it failed as a mission in 1629.
As a regional/public historian, I most often begin my research by looking at maps. They tell so much of a region's history at a glance, and even though I've been doing this kind of research - documenting and sharing the history of the Red River Valley of the South - for close to 20 years, I find compelling information with every new map I encounter.
As I was perusing the astonishing collection within Barry Lawrence Ruderman's "Rare Maps," I came across a map from 1811, "Spanish Dominions of North America" by John Pinkerton. On this map was a little place labeled "San Calixto." I started to look up other maps from this vintage, and they, too, noted "San Calixto" or "S. Calisto."
In maps from 1802 (Arrowsmith), 1811 (Pinkerton) and 1827 (von Humboldt), San Calixto aka S. Calisto appears to the north bank of the Red River near the 98th Meridian and between latitudes 35 and 36. Of course, the cartographers copied off each other, making the location of San Calixto an approximate assumption. I've yet to come across any written documentation for San Calixto, save for the maps.
The co-ordinates place San Calixto in the Wichita Mountains. Thus, San Calixto may be the small Spanish mission in the Sierra Jumanos - the Spanish name for the Wichita Mountains - that has been mythologized by Oklahoma locals as a gold prospecting site. It would also mean that this place was the first evidence of Spanish missionizing/settlement in Oklahoma.
In 1629, Father Juan de Salas of Santa Fe (New Mexico) established a small outpost near the Red River to missionize to the native tribes. Like most tribes along the Red River, they did not take kindly to this intrusion, and the mission failed. However, the Spanish desire for gold led to prospecting, using San Calixto evidently for base of operations. These expeditions apparently took place for at least a century. The first documented expedition was in 1650, and Creole trader Brevel from Natchitoches came with his Caddo cousins to the Wichita Mountains in 1760 and reported "that the Spaniards were engaged in mining operations."*
Legends abound about Wichita Mountain gold (like Frank Dobie's tales!) and many people sought fortune in the granite rocks of the mountains. In 1956, archeologists Eugene Hollon and Sherman Lawton decided to hunt down some evidence of these stories when geologist Harry Feather noted a reference to an "arrastra" - an ore mining drill - located among notations of "abandoned mines" on a map of the area. While the historians found the drill, they concluded that it mostly likely was constructed in the late 19th century by American prospectors.**
The arrastra site, on the National Register of Historic Places, is east of the Cache-Meers Road between Cache and Meers (Comanche County), Oklahoma on the Parallel Forest Trail.
*There has been scholarly doubt cast on Brevel's travels and observations. The quoted line derives from a history written by "Sisters fo the Third Order of St. Fancis, 1855-1928 Vol 40, No. 4" who quoted "History of Oklahoma" by J. Thoburn and I. Holcomb.
** Hollon, Eugene W. "A Spanish Arrastra in the Wichita Mountains." Chronicles of Oklahoma, Vol 34, No. 4. Winter 1956-1957. https://gateway.okhistory.org/ark:/67531/metadc1760987/
1802 Map: https://www.loc.gov/item/2001620920/