At Barretts, Missouri, the first railroad tunnels west of the Mississippi River were built between 1851 and 1853 by the Pacific Railroad of Missouri, later renamed the Missouri Pacific in 1876. They carried a single broad gauge track with 5 feet 6 inches between the rails and were designed by the line's chief engineer, James P. Kirkwood, for whom nearby Kirkwood, Missouri, is named. The tracks were changed to standard gauge, 4 feet 8 1/2 inches, in 1869. This tunnel was originally 450 feet long, but was shortened to 410 feet in 1929. As single-track tunnels on what became a double-track railroad, they created an operating bottleneck that became intolerable during World War II, and in 1944 they were bypassed by two main line tracks placed in a cut about 100 feet to the south. The land with the tunnels then became surplus to the railroad's needs, and the museum leased the property for $1 a year until it was later donated. The tunnels were placed on the National Register of Historic Places in 1978.
