Iron Mountain Baby refers both to a folksong and the subject of that song, William Moses Gould Helms.
On August 14, 1902, William Helms (June 5, 1835 – December 13, 1917), a 72-year-old farmer and civil war veteran, was walking along the St. Louis, Iron Mountain and Southern Railway (later the Missouri Pacific Railroad) where it crosses Big River outside of Irondale (Washington County, Missouri), collecting lumber for a barn he intended to build. He saw No. 4 speed northbound over the bridge. Then, hearing a strange noise and following its source, he found what is described as "an old fashioned telescoping valise." The case turned out to contain a baby, whose age was later estimated at approximately five days. Having fallen about 50 feet (15 m), the child was badly bruised, with a pronounced dent in its head. Helms took the child home to his wife, Sarah Jane Knight Helms (July 10, 1850 – April 15, 1925) and they nursed him back to health.
The child was named for his foster father, Bill Helms, and "Gould," the owner of the railroad, but also "Moses," because he was taken from the river. The story spread throughout the United States, and gave rise to the folksong. Many women came forward, claiming to be the boy's mother. However, when the child was six years old, the elderly couple formally adopted him.
After the death of the elder Helms, William and his mother moved to Salem, Missouri. He attended Braughton's University and Southwest Missouri State Teachers College (now Missouri State University); his education was paid for by the St. Louis Iron Mountain & Southern Railway. He became a printer. On August 5, 1933 he married a woman named "Sally," (September 17, 1904, d. Racine, Wisconsin, September 1987). They had one son, William (died at age 14, according to some sources).