Do Locomotives Have Air Conditioning? Are locomotive cabs heated?

We have written many pieces of content about locomotives

and here is another useful one.
While is fairly easy to admire the exterior of a locomotive, by literally walking to a train station or a railyard, getting inside of one of it, might be harder if not impossible.
Because of that, questions like do

locomotives have air conditioning?

Or do train engine cabs are heated? Get to be frequently asked.
There are many types of locomotives out there, the modern locomotives (built in the last 30 to 40 years) have many features that enhance the comfort of the crew, one of those features is the air conditioning and heating. However this was not always the case.
While older locomotives were always heated with some sort of system, they lacked air conditioning, which can be extremely unpleasant for the train crew, surrendered my heat radiant instruments, in hot environments, think Arizona during summer.
Beside air conditioning and heated cabs, modern locomotives are equipped with a cooler and an ice maker.

A short history of air conditioning on locomotives

Early to mid 1970’s, Santa Fe and Southern Pacific started using air conditioned locomotives on a large scale, being the first railroads to use AC. Both railroads implemented AC on new units as well on their rebuilds, greatly improving train crew working conditions.
The rest of the class I railroads had followed suit with either acquiring AC equipped locomotives or rebuilding the current ones, however they were not in a hurry.