Those photos are quite a find. It does appear that 34" gage would be plausible. Was this clay mining done to make bricks?
I am familiar with the history of a large brickyard in Chaska, MN that had an extensive rail system including side dump cars, 0-4-0T steam locomotives, and Plymouth gas friction drive locomotives. Here is an interesting website covering Minnesota brickyards: [
www.mnbricks.com]
Most of the listed brickyards lack detailed information, but a few have some information and photos. But what is fascinating is just how many brickyards there were that have become all but lost history. There is something appealing about the earthy business of digging up clay, shaping it, and firing kilns to make bricks. People who have studied this brick history can explore the small towns today and find examples of brick buildings made of specific brickyard brands according to their characteristics and sometimes molded brickyard names.
I assume that other states had a similar population of brickyards. This site does list Missouri, but only one brickyard is listed. It is named Mexico Bricks.