Two British 11-year-olds from Liverpool lead a toddler away from his mother, tortured him and tied him to railroad tracks which resulted in him being split in half. Not exactly the wild west image most think of, but it's an example. http://www.nytimes.com/1993/11/25/world/2-british-boys-both-11-guilty-of-murdering-toddler.html

The earliest real-life (more the line of thought you'd associate with this) incident I could find was from 1874, when on August 31 the New York Times reported that a Frenchman named Gardner had been robbed and tied to railroad tracks. He managed to loosen all the ropes but the one that secured his left foot, and the train cut off his leg below the knee. Though he survived to describe the attack, he soon died of his injuries.

There are other examples, including cases involving a kidnapped 13-year-old boy (1881), a 40-year-old mechanic (the article actually uses the word "dastardly" to describe the crime), a college freshman (part of a 1905 fraternity initiation; he died), a 10-year-old boy (1906), and a 19-year-old man (1907).

After this there are a few copycats because "Captain Tom's Fright" published in 1967 already featured the classic train-track death. From what I could find, there are no recorded tied-to-the-railroad track deaths before it was a over the top stage/literary/film short device.