The oldest grade crossing?

[Erik-Gorb-Hamilton]

These wigwags in Port Richmond, CA could be contenders.
https://www.google.co.uk/maps/@37.92496 ... 312!8i6656
Sadly, these wigwags no longer operate since being replaced by gated signals around 10 years ago, these are still on display though.
https://www.google.co.uk/maps/@37.92496 ... 312!8i6656

Again, it has to be in service, and those wigwags are out of service.

Also, do signals where only the old mast is the old thing left in service count? If not, how much stuff can have been replaced on a signal before it's no longer "old"?

And also, the northeast has a bunch of old GRS Type B gated signals still in use, several still with WRRS mini-bells and even the original 8 inch lights and GRS Type B gate mechs.

I'd prefer lights as well but sure, I'll include masts. As for modernization I would say Lights, Bells and Gates, just not the masts or mast locations

[ToledoRailfan]

These might also be a contender, I really would like to head up there and check these out along with the crossings on that Trolley Museum Line.
https://www.google.com/maps/@41.3363257 ... 6656?hl=en

https://www.google.com/maps/@41.3735693 ... 6656?hl=en

https://www.google.com/maps/@41.3830256 ... 6656?hl=en

https://www.google.com/maps/@41.4065886 ... 6656?hl=en

https://www.google.com/maps/@41.4130437 ... 6656?hl=en

[TrickyMario7654]

I think this signal at the Main Street crossing in Pakenham, VIC is the oldest in the state. It was installed in 1938 and remained even though the crossing got gates in 1986. Although the McKenzie & Holland 8" lights are old, they're not the original lights, but I'm pretty sure the actual mast, base and pinnacle are original.
https://www.google.com.au/maps/@-38.080 ... 312!8i6656
https://www.google.com.au/maps/@-38.080 ... 312!8i6656
https://www.google.com.au/maps/@-38.080 ... 312!8i6656

This abandoned crossing in Koo Wee Rup was also really old (and pretty much all original, including a McK&H Teardrop bell and GRS XB/XD 8" lights) but the signals have since been ripped out by NaziRoads.
https://www.google.com.au/maps/@-38.199 ... 312!8i6656
https://www.google.com.au/maps/@-38.199 ... 312!8i6656
https://www.google.com.au/maps/@-38.199 ... 312!8i6656

[ZachL]

I'd say these gates are a strong contender, maybe the signals too.
https://www.google.com/maps/@41.9296215 ... 6656?hl=en
https://www.google.com/maps/@41.9299817 ... 6656?hl=en

https://www.google.com/maps/@41.9285207 ... 6656?hl=en
https://www.google.com/maps/@41.928116, ... 6656?hl=en

Those are likely re-installs, because that's a short/tourist line IIRC

[ToledoRailfan]

I'd say these gates are a strong contender, maybe the signals too.
https://www.google.com/maps/@41.9296215 ... 6656?hl=en
https://www.google.com/maps/@41.9299817 ... 6656?hl=en

https://www.google.com/maps/@41.9285207 ... 6656?hl=en
https://www.google.com/maps/@41.928116, ... 6656?hl=en

Those are likely re-installs, because that's a short/tourist line IIRC

Its hard to say. The Museum was founded in 1940 and before that, the museum's line was an interurban line. I'm interested in how they're aloud to have such old equipment like those gates still be in service on a public crossing.

[freebrickproductions]

Given the clarification from the OP, here are some of the oldest crossings I've been to...
These two in Nashville have some old NC&StL signals at them, though the US&S cantilevers, US&S 8 inch lights, and the US&S Teardrop bell at 19th Avenue are the only original things:
http://www.rxrsignals.com/Tennessee/Nashville/18/
http://www.rxrsignals.com/Tennessee/Nashville/19/

This crossing in Portland, TN has a Transport Products Corp. mast that probably dates from the 1950s, but just about everything else is from the 1960s, it appears:
http://www.rxrsignals.com/Tennessee/Portland/Main/

This crossing in La Vernge, TN also features a pair of old WRRS signals from the 1950s/1960s, though the original bell and one of the gate mechanisms were replaced:
http://www.rxrsignals.com/Tennessee/La_ ... nes_River/

Another old L&N install from the 1960s here in Tullahoma, TN, though the original lights were replaced:
http://www.rxrsignals.com/Tennessee/Tullahoma/Brown/

Christiana, TN also has a really old Transport Products Corp. signal from the L&N, likely installed in the 1950s, with all but the gate mechanism, gate arm, and gate lights being original, though the other signal was replaced at some point:
http://www.rxrsignals.com/Tennessee/Chr ... hristiana/

As far as old signals still in service in Georgia go, here's a few old L&N installs from the 1950s/1960s that have at least one of the original gate mechs intact, though two of them also have the original lights and another has an original bell:
http://www.rxrsignals.com/Georgia/Grays ... raysville/
http://www.rxrsignals.com/Georgia/Marietta/Mill/
http://www.rxrsignals.com/Georgia/Marietta/Waverly/

In Alabama, there's also a few old crossings.
Here's an old L&N WRRS install from probably the 1960s with the original bell and one of the signals having been replaced:
http://www.rxrsignals.com/Alabama/Bridgeport/CR96/

This L&N WRRS install from probably around the same time has had all but the bell and signals themselves replaced at it as well:
http://www.rxrsignals.com/Alabama/Calera/CR84_2/

Huntsville has a couple of old L&N WRRS installs (most likely from around the same time period as well) still in use, with almost all of the original equipment there:
http://www.rxrsignals.com/Alabama/Hunts ... ily_Flagg/
http://www.rxrsignals.com/Alabama/Hunts ... b_Wallace/

Odenville, AL has an almost pure SAL signal at it, from the 1950s at the latest, though its partner across the street was replaced by CSX in the early 2000s:
http://www.rxrsignals.com/Alabama/Odenville/Alabama/

Another almost pure SAL install from around the same time:
http://www.rxrsignals.com/Alabama/Ohatchee/Main/

This one is also a rather similar situation, though the vast majority of the lights at it were replaced:
http://www.rxrsignals.com/Alabama/Ragland/Church/

Irondale, AL also has another mostly pure SAL install from the 1950s at the latest in it as well, though the original bell was replaced at some point:
http://www.rxrsignals.com/Alabama/Irondale/2/

This one in Guin, AL, features a Transport Products Corp. "No Left Turn" signal from the 1950s, most likely:
http://www.rxrsignals.com/Alabama/Guin/US278/

Birmingham, AL has quite a bit of old equipment in use still as well:
RACO cantilever signals from what's most likely the 1960s:
http://www.rxrsignals.com/Alabama/Birmingham/24_2/
http://www.rxrsignals.com/Alabama/Birmingham/25/

And old Transport Products Corp. signal from the 1950s (most likely):
http://www.rxrsignals.com/Alabama/Birmingham/16_1/

Some old SAL installs from the 1950s at the latest (though the original bells and one of the signals were replaced):
http://www.rxrsignals.com/Alabama/Birmingham/50/
http://www.rxrsignals.com/Alabama/Birmingham/56/

And old L&N(?) WRRS install from the 1960s at the latest with most of the original equipment having been replaced:
http://www.rxrsignals.com/Alabama/Birmingham/24_1/

Of course, that's for the crossings that I've been to that are on the site.

[AndyWS]

Love that ancient SAL-era US&S signal in Odenville, designed to be used with a wishbone gate. Too bad it doesn't still have one!

[NathanFromEngland]

Given the clarification from the OP, here are some of the oldest crossings I've been to...
These two in Nashville have some old NC&StL signals at them, though the US&S cantilevers, US&S 8 inch lights, and the US&S Teardrop bell at 19th Avenue are the only original things:
http://www.rxrsignals.com/Tennessee/Nashville/18/
http://www.rxrsignals.com/Tennessee/Nashville/19/

This crossing in Portland, TN has a Transport Products Corp. mast that probably dates from the 1950s, but just about everything else is from the 1960s, it appears:
http://www.rxrsignals.com/Tennessee/Portland/Main/

This crossing in La Vernge, TN also features a pair of old WRRS signals from the 1950s/1960s, though the original bell and one of the gate mechanisms were replaced:
http://www.rxrsignals.com/Tennessee/La_ ... nes_River/

Another old L&N install from the 1960s here in Tullahoma, TN, though the original lights were replaced:
http://www.rxrsignals.com/Tennessee/Tullahoma/Brown/

Christiana, TN also has a really old Transport Products Corp. signal from the L&N, likely installed in the 1950s, with all but the gate mechanism, gate arm, and gate lights being original, though the other signal was replaced at some point:
http://www.rxrsignals.com/Tennessee/Chr ... hristiana/

As far as old signals still in service in Georgia go, here's a few old L&N installs from the 1950s/1960s that have at least one of the original gate mechs intact, though two of them also have the original lights and another has an original bell:
http://www.rxrsignals.com/Georgia/Grays ... raysville/
http://www.rxrsignals.com/Georgia/Marietta/Mill/
http://www.rxrsignals.com/Georgia/Marietta/Waverly/

In Alabama, there's also a few old crossings.
Here's an old L&N WRRS install from probably the 1960s with the original bell and one of the signals having been replaced:
http://www.rxrsignals.com/Alabama/Bridgeport/CR96/

This L&N WRRS install from probably around the same time has had all but the bell and signals themselves replaced at it as well:
http://www.rxrsignals.com/Alabama/Calera/CR84_2/

Huntsville has a couple of old L&N WRRS installs (most likely from around the same time period as well) still in use, with almost all of the original equipment there:
http://www.rxrsignals.com/Alabama/Hunts ... ily_Flagg/
http://www.rxrsignals.com/Alabama/Hunts ... b_Wallace/

Odenville, AL has an almost pure SAL signal at it, from the 1950s at the latest, though its partner across the street was replaced by CSX in the early 2000s:
http://www.rxrsignals.com/Alabama/Odenville/Alabama/

Another almost pure SAL install from around the same time:
http://www.rxrsignals.com/Alabama/Ohatchee/Main/

This one is also a rather similar situation, though the vast majority of the lights at it were replaced:
http://www.rxrsignals.com/Alabama/Ragland/Church/

Irondale, AL also has another mostly pure SAL install from the 1950s at the latest in it as well, though the original bell was replaced at some point:
http://www.rxrsignals.com/Alabama/Irondale/2/

This one in Guin, AL, features a Transport Products Corp. "No Left Turn" signal from the 1950s, most likely:
http://www.rxrsignals.com/Alabama/Guin/US278/

Birmingham, AL has quite a bit of old equipment in use still as well:
RACO cantilever signals from what's most likely the 1960s:
http://www.rxrsignals.com/Alabama/Birmingham/24_2/
http://www.rxrsignals.com/Alabama/Birmingham/25/

And old Transport Products Corp. signal from the 1950s (most likely):
http://www.rxrsignals.com/Alabama/Birmingham/16_1/

Some old SAL installs from the 1950s at the latest (though the original bells and one of the signals were replaced):
http://www.rxrsignals.com/Alabama/Birmingham/50/
http://www.rxrsignals.com/Alabama/Birmingham/56/

And old L&N(?) WRRS install from the 1960s at the latest with most of the original equipment having been replaced:
http://www.rxrsignals.com/Alabama/Birmingham/24_1/

Of course, that's for the crossings that I've been to that are on the site.

Whats the NC&StL?

[freebrickproductions]

Love that ancient SAL-era US&S signal in Odenville, designed to be used with a wishbone gate. Too bad it doesn't still have one!

I personally wouldn't be surprised to find out it still had one a few years back. From what I understand though, the FRA mandated to removal of all wooden gates here in the US a few years ago, though a few do still survive in use. Either way, I'm still glad the old US&S signal survives.

Whats the NC&StL?

The Nashville, Chattanooga, & St. Louis Railway.

[dan the ca railfan]

these could be contenders

https://www.google.com/maps/@34.0000181 ... 384!8i8192

https://www.google.com/maps/@34.0008294 ... 384!8i8192

https://www.google.com/maps/@34.0029452 ... 384!8i8192

https://www.google.com/maps/@33.9974648 ... 384!8i8192

https://www.google.com/maps/@33.9993679 ... 384!8i8192

https://www.google.com/maps/@34.0048117 ... 384!8i8192