At a guess, running boards started as simple design transfers from horse-drawn carriages, railroad cars, and the like. It probably was not an accessory, but a necessity in some early car models. While the step height is important, there's also the awkward access into and out of the interior. I.e., one would want something firm and predictable to put a foot down on while making a complicated "lift and twist" motion.
That riding on running boards is illegal is a modern perspective. Since running boards historically probably were not covered by laws disallowing use while moving, the article might benefit by giving some sense of how the use of running boards changed.
I think the idea of running a board served multiple purposes, including the structural strength and acting as side-bumper. Use for carrying items especially prior to 1930 when cars typically had no roof (and earlier cars were just a basin with no trunk or rack) seems a side-effect, though we see it as accepted practice for spare tires or boxes and Google archive of Popular mechanics shows how to mount your dog cage or bag on the running board. More acceptable too in era before highways existed and top speed was 0mph. They may also just be a manufacuring quirk, that Ford found it faster to produce the fender structure that way -- I note the earliest Model T runabout and race cars came without fenders or running boards. If auto running boards had just been to step on they would have at least some of the time done nerf boards or steps as some horse carriages and railroads did rather than a full run between articulated fenders. Markbassett (talk) 15:01, 8 August 2013 (UTC)
United States National Electrical Code
The NEC mentions running boards for, at minimum, exposed NM electrical cable with respect to securing (fastening) it when run at angles to (usually perpendicular to) floor joists. (The other option is to bore holes through the joists and feed the cable through those holes; somewhat impractical after construction is complete due to close spacing of joists.) Obviously this has nothing to do with automobiles. I'm not sure how this should be incorporated...such as creating another article describing that, moving this one, and constructing a disambiguation page; or creating the page for that and adding an annotation near the top of this one notifying the reader of a possible other meaning of the phrase. I could imagine what the NEC meant, but I wanted to research that on Wikipedia.
- If the info you'd like to add is short, the other word sense could either be added to this article, or to a new article, say "Running board (electronics)", as a stub. If there's more than 50 words or so, a new article is probably appropriate. Alpha Ralpha Boulevard (talk) 05:12, 27 November 2010 (UTC)