Small rivers with the most historic bridges

[mcdonaat]

Noticed today while "armchair roadgeeking," aka Street View surfing, that the Pearl River has TONS of old bridges crossing it.

In order of south to north:
US 90 swing bridges (3)
MS 28 truss bridge
Rosemary road truss bridge, possible old railroad span
Byram swinging bridge
Old MS 25 bridge north of Jackson, MS

The Boeuf River in Louisiana has three old truss bridges crossing it.

Any other rivers littered with bridges from a time gone by?

[Alps]

Mississippi River, Ohio River. Is there a qualification for density in terms of bridges per mile, or just overall number?
East River, NY
Oklahoma, Arkansas, and Missouri have so many old bridges that some of the rivers there must also qualify.

[NE2]

Find something in a canyon that an old railroad keeps crossing from one side to the other.

[mcdonaat]

Sorry, should have specified - small rivers, as in rivers that go through, at most, two states. The Pearl River qualifies, as do the Boeuf, Tombigbee, Tensas... smaller rivers in both width and length.

[Alex]

Noticed today while "armchair roadgeeking," aka Street View surfing, that the Pearl River has TONS of old bridges crossing it.

In order of south to north:
US 90 swing bridges (3)

You can throw in the three 1933 pony truss bridges along U.S. 90 as well:
West Middle [Pearl] River
Middle [Pearl] River
East Middle [Pearl] River

[empirestate]

Sorry, should have specified - small rivers, as in rivers that go through, at most, two states.

Oh, well then you want the Hudson. :-)

Seriously though, if by "historic" you simply mean old, then I'd guess somewhere in New England. Rivers like the Housatonic or the Merrimack will have their share of older bridges, although you might have to go smaller still to find one where most haven't been updated yet.