My understanding was when the fruit boats came into Baltimore's Inner Harbour, which until the last 30 years was a working port, the Arabbers bought the over-ripe fruit from the ships and sold it thoughout the city. I can remember when I was a child and lived on the northern edge of Baltimore, you would hear the Arabbers calling "Straaaaaaaaawberries, Waterrrrrrrrrmelon, Straaaaaaaaaaaawberries, Waterrrrrrrrmelon". It was always so exciting the see the ponies and their carts.
The Arabbers' carts are generally either yellow or red. They are loaded with fresh produce and have a scale to weigh the produce. I always try and get something from the Arabbers, because if I, and everyone else, don't support them, this venerable and vulnerable tradition will die out.
There are stables for the ponies and some of the Arabbers also live there, but I've never visited them. By the way, Arabbers is pronounced with a long "a" at the beginning.
P.S. I got a comment that this isn't politically correct. Please follow the Arabber link to learn more about the history of the Arabbers in Baltimore. I admire these people and buy produce from them when I see them. I am not being derogatory in calling them Arabbers, it's simply what they're historically called. I am trying to introduce people to Baltimore in general, and Pigtown specifically. This is part of life here.