Lenny and the List
To answer you question on Center Sidings I had to do a little research in the 1966 track charts(the last set the Q put out )
Center sidings were a siding between the two main tracks and were accessible from both ends and off both mains. I do not have a lot of employee timetables for the La Crosse Div but could not find anything on the movement restrictions on them
Starting at Savanna MP 145 the line along the Mississippi and in a lot a areas was built right on the foot of the bluff along the river
originally built as single track in 1886 the second main was put in in the 1913-15 era to La Crosse and 1928-29 north to St. Croix
Center sidings were at Potosi MP 198-199.3
Cassville MP 211.7-212.9
Bagley MP 227-228
Ferryville MP 262.3-263.5
Stockholm MP 371.3-372.4
Hager MP 389-390
There was a center siding at Monmouth just west of Galesburg on the line to the west but this was not built like the La Crosse Div. sidings as it had regular style switches while the La Crosse Div Center Sidings had like wye switches to speed the entrance and
or exit from the sidings to the regular switch on the main. Today most have been removed leaving a wide spot between tracks. The La Crosse Div also had narrower track centers and there fore restrictions for meeting and passing wide loads.
The Center Sidings provided a more flexible siding accessible to both mains where an inferior train could pull in and clear for the faster superior trains and were put in just before the Zephyr Era started.
Monmouth was often used to set out cars for the Switch eng there or as in the case of the St. Louis beer cars that bypassed Galesburg Yard on a thru train from St. Louis heading west to be picked up by a hot-shot westbound for quicker delivery points west.
authors note: I often write with the idea you need to think when you read
Steve in SC