Most of T43N,R6E is in St Louis County. The township's southwest corner is where the two lines cross just above the word "Elm" at the bottom center of the map. Those two lines mark the western and southern township boundaries. The townships northern and eastern boundaries in Jefferson County are the Meramec River.
My apologies for the large splotch on the right side of the map. This was the result of wide, heavy crease in the map I scanned, and I couldn't get a better image that this one.