Postcard depicting Chicago underground electric locomotive. The original caption reads: "Electric Locomotive in Underground Tunnel, Chicago".
V.O. Hammon Publishing Co.
~1908. No date on postcard but see <a rel="nofollow" class="external free" href="https://archive.is/s5d6I">https://archive.is/s5d6I</a> for the same postcard on sale with 1908 postmark.
own scan of postcard