For nearly twenty years, from 1900 to 1918, Nantucket was the only place in the nation that successfully fought encroachment of the automobile within its limits. Opposing politicians on the mainland and large property owners, mostly non-residents, Nantucketers kept the island free of the "gasoline buggy" until the final vote of the town on May 15, 1918. By the narrow margin of forty - 326 to 286 - the automobile was allowed entry.
Clinton Folger was the mail carrier for Nantucket. Because cars were forbidden by the town, he towed his car to the state highway for driving to Siasconset: http://commons.wikimedia.org/wiki/File:Horse_drawn_US_Mail_car.jpg
But why do the next two cars appear to have been changed to make a seat for the horse driver where the radiator should be?
Brilliant and wise reader angyl_roper (if your email was available on your profile or any of your 3 blogs, I'd email to thank you!) used the comment feature to tell me that: "During the Depression, Ford sold a conversion kit so that you could use a horse to pull your car since fuel was too expensive. I believe this was for the Model A primarily, but also for the Model T. (so why work your horse so hard, instead of just riding the horse and leaving the car at home?)
However, I'll also note that the top two pictures are snowy and it could just be that hitching up horses (and a sled, in the second one) was an easier way to get your car where you needed it than driving it there.
Cedar Knoll Farms commented:
Angyl Roper is right - during the Depression, fuel prices became so hard to keep up with that many people, particularly those in the deep south, were forced to "modify" their cars and trucks, sometimes completely cutting out the front end of the vehicle, and hooking horses and mules to them. These became known as "Hoover Carts", after the president who was blamed for the economic downfall.