Yes, it is. But as I see it, it only clarifies what is the first "subway" nation-wide, regardless of the fact that it contained streetcars or rapid transit trains. "Subway" has to be taken as the general meaning which most would accept here, an underground way used by passengers or freight by railways. We lose the "oldest" title the moment that we interject the pedestrian use. (Those below street and track level pedestrian crossings such as at the Roslindale Square Commuter station are "subways", also.) You run into the same problem with "tunnels", even more so.
~Paul Joyce~
Moderator: Toy Trains, Model Railroading, Outdoor and Live Steam
Paul Joyce passed away in August, 2013. We honor his memory and his devotion at railroad.net.