what did rail workers do - who installed the rails in the beginning ?

Everything with their hands.

Everything by hand.

You really have to see the old pictures at the museum to get the whole picture. They needed a way to move freight (and people) from Baltimore to the Ohio River. The B&O canal was already working on extending the canal (horses/mules pulled boats thru man-made canals...VERY slow...A few businessmen and railroaders decided they had to beat them there to secure the business. The race was on....