RPO Cars, Where Did They Run?

First, the CZ never carried an RPO.

RPO's would generally be captive on the home road, but mail storage cars (baggage cars, converted troop sleepers, etc.) could wander far afield.

Rusty

Sleeper cars and baggage cars did travel cross-country on other than home roads.  There were not that many of them that provided this service.  Coaches and RPO's kept to their home roads.  Someone is sure to point out an isolated exception but the railroads made money on their individual mail contracts.  Cross-country mail originating in say, Philadelphia and bound for Los Angeles would have been sorted on a Chicago-bound Pennsy RPO into a bag bound for L.A. (or maybe California in general, I'm not sure).  In Chicago, that bag would have been transferred onto a train headed further West, perhaps on the Santa Fe or Burlington.

You might also Google "Railway Post Office" and read the various history and route information.

Unfortunately, I was afraid that I correctly understood that RPO's were kept at home.

I guess I will just have to switch in an out those of the roads that ran into Denver.  Fortunately, that includes several roads...the D&RGW, MP, CB&Q/C&S, RI,

D&SL, and ATSF.  Not sure about the UP, or whether the Denver and Intermountain

electric interurban ran RPO's. These all standard gauge...there were additional narrow

gauge lines over time, too.