Railroads got massive subsidies in at least two forms: huge land grants, and the power of the U.S. Army to wage war on the native peoples who otherwise would have stood in their way.
The land grant thing is sort of weird though. Hard to think of it as that big of a subsidy when the land was so so low in value prior to the railroad and the railroad's construction is what made the adjoining land so valuable. I wouldn't call it a subsidy at all -- but rather an investment that turned nearly worthless land into much more valuable land and attracted much more investment dwarfing the original "subsidy"
