I recently found that MO now has online historic aerial surveys. Most available are from the 30's and 50's but I'm trying to search and see if I can find any remnant of the old track lines. I've got a good idea of where this initially would have ran but would like some visual confirmation.
As for bricks, the counties around Rosebud, MO are still dotted with many small clay pits that were indeed mined for both bricks and fireclay. Some are still owned/worked by major refractories. St. louis also had a number of significant clay mines and brick factories. This
link talks about that.
Here are also some historic pics of clay pits from around this region. Legend has it that MO clay was used in several NASA launchpads.