Research: Jeff Kitsko. Photo credits: John and Barb Bee; Doug Kerr; Robert Mortell; Denny Pine; Adam Prince

We'll start with US 6: when the US routes were first commissioned in 1926, the west end of US 6 was in Erie. It more or less followed its current route to Union City, but from there it was routed northwest along modern-day PA hwy. 97, and then PA 505 in Erie, ending at US 20. The photo below shows that spot:

Bees

That was once where US 6 ended. That's probably also where US 120 would've ended during the very brief period when it went as far west as Erie. In the early 1930's, US 6 was extended more westerly from Union City (along today's US 6N), and its old route from Union City to Erie became US 6N [II]. So the photo above shows the endpoint for that route as well.

But that lasted only for a few years, too: in the mid- to late-1930's, US 6 was rerouted again, this time along its present course through Meadville. It's "intermediate" route between Mill Village and West Springfield became US 6N [III], and US 6N [II] leading into Erie was decommissioned. Since that time, only one US route has ended in Erie: US 19, which has been serving the city since 1926. Originally US 19 followed Peach Street past its junction with US 20 (26th Street), ending somewhere downtown. Despite a reroute south of town in 1928, US 19 continued to use Peach until 1932. That year, the US 19 designation was changed such that it followed today's PA 97 into town. PA 97 used to end at the same intersection where PA 8 ends today; below is a photo:

Pine

That was the north end of US 19 from 1932-1936. That was the year US 19 was rerouted onto Peach again, and its endpoint has been the same ever since: at US 20. The view below is north on Peach, just before its junction with 26th:

Bees

The photo below is looking west on 26th:

Prince

It's kind of hard to see, but the signs show that westbound US 20 continues straight ahead, while the next left (at Peach) will put you at the north beginning of US 19. Below is a shot from the opposite direction:

Kerr, Dec. 2002

If you turn that way, the first southbound US 19 marker looks like this:

Mortell, 1998