Surely this was a streetcar, not a bus? I'm an English viewer but like to think I know the difference!

[As noted in the caption, it's a trolley, but some other commenters have overlooked that. - tterrace]

One of the first rules of etiquette my Mom taught me was to always offer a lady a seat on a public conveyance.

It didn't matter how tired or hard worked you were no lady was allowed to stand while any of her children were sitting down.

You would have thought back in the day that those gentlemen would have offered their seats to those ladies having to stand in the aisle of the trolley compartment.

Yup, that's where the term comes from to describe people at meetings and other functions that are "just there for the ride"!

Is the man in the lower left corner smoking a cigarette, or does he simply have an unlit cigarette in his mouth? I want to say smoking was not allowed on the bus, but say it was -- where would you ash (or put out) your cigarette on such a crowded bus?

[On the floor. - tterrace]

On the positive side -- given that a few years later, Baltimore would close its public swimming pools rather than racially integrate them -- several African-American passengers seem to be sitting near the front of the bus. On the negative, the smoker in the first row is taking a few seconds off each of his fellow passengers' lives, with apparent impunity.