Endpoints of
US Route 51

It appears US 51 began using 2nd in about 1935, and it probably never ended on 2nd at Silver.  That was about when US 2 was rerouted to stay on Cloverland Drive in Ironwood MI (the city directly across the Montreal River), which meant the new highway aligned to the north of downtown Hurley.  As a result, US 51 had to be extended north in order to junction the "new" US 2.  3rd was not a through road, so US 51 traffic was shifted over to 2nd, where it has remained ever since.  Here is how the "End" assembly looked historically...

...and in case you missed that one, there was another just ahead...

Visible to the right is what was once a high-speed slip ramp leading to northbound US 51.  Today that only provides access to a business, and then it is barricaded.  But the road itself continues, and on the far side of the barricade it is now known as "Circle Drive".  It still connects to Main, but it is no longer a one-way ramp; it functions as a normal neighborhood street, providing access to a few private residences.  Continuing ahead on Airline, we come to the junction with Main itself:

The south beginning of US 51 was to the right.  But in 1986, US 51 was rerouted along a newer alignment which bypasses the "Old 51" neighborhood.  The newer highway begins at the next traffic signal; here is a close-up view of the signage there:

That's more of a standard 4-way intersection; one cannot make that right-hand turn at the same rate of speed as they could onto the old US 51.  The cars visible in the foreground of that photo are at the south end of US 51; they were viewing the perspective shown here:

Now, heading back the opposite direction (east on Airline), here is the signage at the beginning of modern US 51: