I just gave you a “Great Question” upvote. I love your question, have no idea about the answer, and look forward to learning.

All I know is that I’m sure it wasn’t the infamous Ford Edsel, which nobody wanted even if you left the key in the ignition.

According to this: “In 1949 the Chrysler Windsor was put into production and the first key start ignition was put into standard production.”

I remember that, because it only took some scalawag about 3 seconds to steal my brand new 1948 Studebaker! ;-o

Google is your friend:

https://www.bosch.com/stories/history-car-locking-systems/

https://daseuropeanautohaus.com/evolution-of-car-door-lock-system/#:~:text=The%20first%20types%20of%20car,home%20locks%20at%20the%20time.&text=The%20main%20reason%20separate%20keys,became%20a%20relatively%20easy%20process.

Looks like you have your answer. As an aside, there is a car museum in the Tampa Bay area that has a lot of automobile firsts. The owner is obsessed with significant automotive innovations over the years. The docents are amazing, tons of knowledge. It’s not a very large museum, but definitely worth seeing if anyone on the Q is ever in the area.

Here’s the link https://www.tbauto.org/the-collection/

Up until the early 50’s, it was possible to attach a wire from the positive post on the battery to the ignition coil. (At least on some cars/trucks)To engage the starter was only a matter of pushing down on the starter pedal that was located just above the gas pedal. Column locks for steering didn’t come around until the late 60’s/early 70’s.
You could start cars without column locks by crossing a hot wire to the ignition and shorting out the starter (on the starter) between the hot post and the solenoid wire.

Remember when cars had two keys? One for the door and one to start the car?

I remember then the trunk had a different key (usually round) than the ignition (usually rectangle or square)