906 day (September 6) celebrates the area code of the Upper Peninsula of Michigan. First I've heard of this holiday, but I heartily approve.
In honor of this day a couple of nice photos of Marquette, MI came via Shorpy. The photos of the harbor and ore docks, Front Street, and a panorama of downtown Marquette date from 1908 and 1909 and are from glass negatives from the Detroit Publishing Company.
A detail below shows the Hotel Janzen, with a train's smoke just to the left of it and a piece of City Hall at the far left.