San Luis, or Saint Louis was Louis IX, the King of France who was a devout catholic and led several crusades in the late 13th century, dying on the 8th crusade from dysentery. Pope Boniface VIII made Louis IX a saint in 1297 with his feast day being next month on August 25th. A number of places in the region are named after him, so it is not just the city and the central Mexican State in Latin America with a surprising French connection. The reason for establishing the first Spanish settlement in the state the Cerro de San Pedro and its productive gold and silver mines and this is recognised on the State coat-of-arms which depicts Saint Louis standing on a hill flanked by two silver ingots and two gold ingots. Potosi was added to the name, at a later date, in reference to the famous silver mines in Bolivia probably highlighting that Mexico had an (almost) equivalent!
The note representing this bank is 1 peso example from the final issue. The front of the note, as for all denominations, displays the State coat-of-arms and on the left is a vignette of the bank headquarters building, all 1 peso notes are Series D and dated 15th February 1914. The back of the note features a central image of the Mexican coat-of-arms and, on the left, the stamps indicating the 1% duty had been paid allowing the note to be issued.
San Luis Potosi therefore becomes Mexican State No. 9.