I’m wondering how the front door locks are supposed to work. I can lock them when I’m inside the vehicle (have rolled down the window and tried the handles–they both lock), but if I step out and push the handle forward then close the door, the door unlocks itself. I don’t actually have a key for the doors, so I can’t lock them from the outside either, which means that until I get the locks changed, it’s a good thing I can’t lock myself out of my vehicle! But I’d like to know how it’s supposed to work. Once I get working locks and keys, it would sure be more convenient if I could lock the door from the inside then push it closed rather than have to lock it with the key.
You have to lock it with the key, it doesn’t work any other way…
Bob
Nanno, If you are looking for new key lock cylinders for your 59, I just bought some a month ago that was a matched set of 2 door cylinders and the one matching ignition cylinders insert from an ebay vendor in Detroit area. I installed them last weekend and they work and look great!
His handle is “MasterKey03” on Ebay. They can go at auction from $60 to $100 . All I had before was a ingition key that did not fit the doors at all. Nice having them all keyed alike.
John Q.
Bob, thanks for the info… it’s good to know my door is working properly (even if it would be more convenient once I get keys to be able to lock the door and shut it).
John Q, I’m hoping to see the locksmith early next week. Unfortunately I’m looking at perhaps having all of my locks changed. It appears that the key to unlock the trunk and doors (and glove box) was lost at some point in the car’s past, so the owner changed out the lock on the trunk only. The trunk has a different style of cylinder than the rest of the car and the key doesn’t work on any other lock, and so far I can’t find anyone who has a blank to match it. I’d like to get new locks all the way around. I don’t really care if they aren’t “original” to the car so long as they fit and I can get keys made for them. I don’t like taking a key to get copied only to have the clerk look at my key like it’s of alien origin. Do you know if it’s possible to re-do all the locks with something that isn’t specifically made for the '59 Plymouth? It seems that would be the easier (and cheaper) route if it’s possible. I’m not a huge fan of keeping something “original” if it’s not also (somewhat) practical. She may be flashy, but ultimately my “Geraldine” is a work horse, not a show animal. 
Nanno, it is “normal” that the trunk has a different lock than the doors. In all 59’s you had two different keys, 1 for the doors and ignition and one for the trunk and the glove box (if it had a lock). The set on Ebay is for the ignition and 2 doors and includes keys, not a bad deal for $60 in my opinion. Installing the new locks is easy but if you can’t do it yourself it wouldn’t cost much to have it done in a garage.
Ron
There are several blanks keys on Ebay, like Pardon Our Interruption... I couldn’t find any auctions by “masterkey” right now.
Ron
Well apparently I’ve got three different locks. The ignition key doesn’t work on my doors.
News Flash!!! The Ebay seller I was trying to post his Ebay handle on is actually: Masterkey03 (his name is Jordan)
I seemed to once again,not check fully what his correct handle was on Ebay. He does have some current non-mopar locks for sale now and if you send him a message on one of the current auctions about your 59 Plymouth needs he can work up a set for you. That is what he did for me. And I had communicated my needs thru one of these other auctions for what I wanted.
Also, just about any later 60’s and 70’s trunk locks will work for your car. The original style has the key entry entrance off to one side and not in the middle of the cylinder like later 60’s and 70’s car. But any trunk style will do. As long as it has the long tang device coming off the back of it that goes thru the actual trunk latch. You can trim the tang down if you get one that is longer the what is needed. Some of these trunk cylinders on ebay sometime comes with 3 or 4 different length tangs for you to choose from
The 56,57 & 59 Plymouth style, with the lever on the back of the cylinder is the type that works with our cars.60’s and laters version is slightly different.
On Ebay, there is an occasional sale on key lock glove box latches from other sellers. So keep and eye out for them during your ebay searches. 
John Q.
Thanks for the information!
I sure understand the modern convenience of pre-locking your door, so you don’t need to dig out your key to lock the door.
Late '50’s Mopar thinking was to REQUIRE you have keys in hand in order to lock your car. This way you don’t lock yourself out.
While I was only 3 yrs old in 1959, I think it was common practice for folks to leave the keys in the ignition or above the sunvisor when they left the vehicle.
As for buying new locks, why not inquire at your local locksmith first…You need not change the entire lock assembly. Decide which key you want to use, and take the non-working locks in for a re-setting of the pins. (That’s what I did anyway).
Of course if your locks are worn out or something, head for eBay.
I’m not sure how long they kept it that you had to lock the door with the key,I had a 64 Fury 3 and a 65 Fury 1, and with both these cars you had to lock them with the key…
Bob
I wasn’t aware it was anything BUT, until I started work here in Seattle in 1990 with a company that used older Ford trucks. They would lock if you held the exterior button “in” while closing.
I took my car to the locksmith, and he can change the pins in the lock so my ignition and doors match, but we’re having one problem. We can’t seem to get the lock cylinders out of the car doors. It seems there is a little clip that needs to be pulled so the locks can be removed, but we spent all afternoon trying various tools and couldn’t seem to budge them. They’re stuck in there good. Ron (the locksmith) sprayed the locks down thoroughly with some Houdini lock un-sticker but he still couldn’t get them to pop free. Is there some other trick to it? Do we have to remove the outside door handle first? It would help if we could actually see inside there, or if the access holes were bigger and more conveniently located.
Dang, sometimes I wish I still had all the car parts I used to have…I could easily have posted a photo and explanation…
But hey, Life goes on.
The locks are held in with a “slide clip”, a simple springy one for the trunk lock, and more complex ones for the doors.
go to next post..
Roger,is correct on the tab. Since i just installed these in my car it is fresh in my mind. To slide the tab towards you, (away from the front of the car, will slide it a bout a 1/2 inch or less, you don’t take this tab out but just slide it by pulling it to you. When you re-install you insert the key cylinder and push the tab in (towards the fron to the car or hinge area) and it locks it into place. The travel of this tab is minimal.
Taking the door panel off helps to see this area. If you have the main 57/58 Yellow Factory Service manual a great view of this is on page 406. On page 405 it shows you to undo the adjusting pawl that attachs to the door handle to gain better access. This is thru the inner jamb area that has the door catch on it.
If you knock this tab off, you can re-install but in required me not having the door handle in to grap and position this tab back on. Do spray liberally with WD-40 due to the crusty conditon this part generally has being exposed.
I will try to take a picture of this area to see if it helps visualize the slide tab.
John Q.
page 406, detaching the handle pawl, you may or not have to do this. if it is in the way the detach it.
page 407 pulling or pushing the tab to unlock or lock the cylider to the door outer shell on the inside.
picture of locking tab inside the door from window access port (remove door panel) my glass is not installed yet. Also the key lock pawl to door latch is also not installed either at this point.
Thanks, as always, John. Your pics remind me the door lock retainers are a bit more complex than the trunk lock retainers. The door lock retainers are a sort of self-contained mechanism, although it isvery difficult to see this from John’s pictures.
Use a flashlight, and look for the upright “tab”… 
Thanks for all the help, you guys. The visuals are great. I’ve got the door panel off on the passenger side and have had a good look at that lock. The bracket is a little bent, and I suspect that this is not helping me slide the thing over. I’m also having a hard time getting a good enough purchase on that tab to keep my tools from slipping off it when I give it a good solid pull. I may spray some more lube in there and leave it for a couple more days and see if that helps. I do have the yellow shop manual, but it makes this whole procedure look annoyingly simple compared to how it’s playing out in real life. I suppose that’s to be expected with anything that has 50 years worth of crust built up on it.
In the meantime, having the panels off the doors is a good time to clean out the goop piled up in the bottom of it. It’s disgusting and it’'s plugging the drain holes. I’m afraid my doors will start sloshing after I wash the car if I don’t get them cleared out so the water can drain!
Revised:
The trunk lock is held in place with a springy-metal clip.
These “clips” have a right-angle bend (tab)…at one end. Use this tab to place a screwdriver against and then tap it (sometimes hard!) to slide it off.
The door lock retainers are a bit different. The doors have a slot to access the tab. For the door locks, you must PULL on the tab.
Maximum movement on these sliding clips is ~ 1/2" or less.