The St. Louis, Iron Mountain and Southern Railway (St. L., I. M. & S.), commonly known as the Iron Mountain,[a] was an American railway company that operated from 1856 until 1917 when it was merged into the Missouri Pacific Railroad.

They were forced out through Jay Gould's railroad monopoly.

[1][2] In 1883 the railway was acquired by Jay Gould, becoming part of a 9,547-mile (15,364 km) system.

It was robbed twice, once by the James-Younger Gang, on January 31, 1874, at Gad's Hill,[3] and once by the "One-Time Train Robbery Gang", on November 3, 1893, at Olyphant, Arkansas.

[4] A heritage railroad by the same name, based in Jackson, Missouri operates about 6 miles (9.7 km) of shortline in Cape Girardeau County.