It isn't: many "Metro" systems have tracks that are at ground level, just like main line railways. The term derives from the Metropolitan Railway in London, the first underground railway in the world, opened in London UK in 1863. It was followed in 1871 by the confusingly-named Metropolitan District Railway - also in London - and then by the Paris, France. system in 1900. This was built by the Compagnie du Chemin de Fer Metropolitain de Paris, and always known to Parisiens as "Le Metro". Since then, the term "Metro" has been applied to many similar urban railway systems with closely-spaced stations and a frequent service of trains. Indeed, twenty years ago, many of the inner-London services of the national rail network were for a time designated as "Metro" services. However, other terms are used, such as "Underground" or "Tube" for the services run by London Transport; "Subway" in New York USA, or "U-Bahn" in Berlin, Germany, for example. All of these systems have lines that run on the surface as well as in tunnels or elevated on viaducts.

Since such systems were built to solve public transport problems in already built-up cities, it was both cheaper and convenient to build them underground in the built up areas, or elevated over the streets on viaducts, such as the famous "El" in Chicago - another interchangeable term. Out of town, it is cheaper to lay them on the surface, just like ordinary main line railways

Walking pace over uneven terrain and fording rivers is a little slower
8-20 miles a day is a more reasonable estimate for 1800's travel cross country.About 2 miles an hour. Detours around hills and getting to crossing places on the streams and rivers. Rest periods for the horses or mules. Rest days for the horses.and to make repairs. Back then most would not travel on the Lords Day. Breakdowns along the wheel . Stops for things like wheel repair. A minimum of three months. Rain days would mean mud and most would have to stop depending on terrain and need to wait for it to dry a bit.
3-4 months travel time.

http://www.fhwa.dot.gov/infrastructure/b...

If they had to pay a toll to use a bridge or Ferry. Back then the price of few dollars was a months wages.

Part of this would be crossing the Appalachian Mountains which even today have limited roads . Much forested lands and swampy areas.

Yes and no.
There are no regular steam trains on Russian railways. However, there are some still running, and quite a lot preserved in museums or on stationary display.

Here's a link to a Russian steam service - it's a private company, offering expensive luxury travel.
http://www.goldeneagleluxurytrains.com/a...

Here's a link to a site which lists some of the surviving locomotives:
http://www.internationalsteam.co.uk/trai...