We’re not sure if this is part of Chicago’s underground street system, now unused, which was used to expedite deliveries and at the same time to reduce traffic congestion on Chicago’s street-level. We believe that underground systems – including pneumatic tube systems – have in some places been prematurely abandoned. They reduce congestion (waiting time and reduced speeds are responsible for a large share of the pollution generated by vehicles), speed delivery, and reduce costs for everyone. Here’s an early photograph of rail-based mail processing in Chicago.