|A.J. Russell image of the celebration following the driving of the "Last Spike" at Promontory Summit, U.T., May 10, 1869. Because of temperance feelings, the liquor bottles held in the center of the picture were removed from some later prints.|
The first railroad in America was the Baltimore and Ohio Railroad, chartered in 1827. As a side note, we recently viewed the Charles Carroll House here in Annapolis, Maryland. In 1830, Charles Carroll was the last surviving signer of the Declaration of Independence and he laid the first stone when construction on the track began in Baltimore on July 4, 1828. See AmericasLibrary.gov, "First U.S. Railway Chartered to Transport Freight and Passengers, February 28, 1827."
Many occupational records have survived but finding them can be a challenge. My own ancestors lived in Northern Arizona and worked for the railroad to provide cash for a large family. Their construction experience likely led to their later involvement in road construction and my uncles founded what became, at one time, one of the largest businesses in Arizona. However, if your ancestors worked for the railroad records of their employment could be in an archive or another historical repository such as a railroad museum.
To start your research, you may wish to investigate exactly where your ancestors lived and whether or not they were near a rail line. Millions of Americans worked for the railroads and records of their employment are scattered from the U.S. National Archives to local libraries. Here is an example from the National Archives: