Our good friend Ludwig down in Georgia asked why the width of US railroads is such a strange number. Definitely 4 feet 8.5 inches is odd at first look. There have been lots of pseudo answers to this question. I found the most common on the Internet at Yahoo. Answers.
" This story is a "We've always done it that way" tale. It says that the standard distance between railroad rails in the U.S. is four-feet, eight-and-a-half inches. Why? Because that's what it was in England. Why? Because that's the gauge the tramways used before the railroads. Why? Because the tramways were built using the same tools as wagon-builders and that's how wide the wagon wheels were spaced. Why? Because the old roads in England had ruts that the wheels needed to accommodate. Why? Because the ruts were made by Imperial Roman chariots.
Or the simple answer of " the width of two war horses asses" which is not always a good explanation in mixed company or around teen agers (insert lots of giggles here).
BUT history of the US railroads shows that from the beginning of railroading until after the Civil War the width between the rails varied between railroads. This of course made shipment of goods really difficult. Interchanging between railroads ment unloading the goods and then reloading them. Today with standard gauges, rail cars are simply 'interchanged' between railroads.
Sometime after the Civil War the US Government finally decided to standardize the 'gauge' of US railroads to the present 4'8.5".
BUT that is just main line railroads. At the Baltimore Streetcar Museum we learned that their 'gauge' is a little different and for a reason. The story that they tell is that railroads we're notorious for sneaking onto other folks right of way in the past. If you have ever been to Baltimore, especially in the Fells Point district, you know that there are tracks in the streets all over the place. Some railroad, and some streetcar. The City decided that to stop the railroads from using the streetcar tracks they would make the gauge 5 feet.
AND mining and logging railroads are usually a 'narrow gauge' since the tracks are easier to lay and most times are only temporary.Of course the standard size of a modern day chariot is far different.