Brock's Gap is a pass across the ridge of Shades Mountain used by Native Americans and early settlers. The gap was surveyed by John T. Milner and selected in 1858 as the route for the South & North Alabama Railroad. It was named for Pinckney Brock who had purchased the land the same year.
In order to prepare the gap for use by the railroad a 75-foot deep cut was made, primarily by blasting through beds of limestone with nitroglycerin. It was hailed, in the 1850s, as the deepest railroad cut in the world. The onset of Civil War interrupted work on the cut and the pass was used by Wilson's Raiders on their way to Oxmoor Furnace. The cut was finally completed by Bartley & Boyles of Helena, with J. F. B. Jackson as superintendent, in 1871.
The work gangs that carried out the hard labor to complete the work were originally made up of slaves, and later of convicts. Contemporary accounts described cruel treatment and hasty burials of those who died at the site. Later residents in the area have reported hearing chains rattling and moans from the area of the cut.
Another railroad cut in the vicinity, for the Atlanta, Birmingham and Atlantic Railroad, was completed in 1907. At the same time, the Louisville & Nashville Railroad, successors to the North & South, improved their grade profile by digging the South Shades Crest Tunnel, bypassing their Brock's Gap cut. Part of the L&N cut was subsequently backfilled for the crossing of South Shades Crest Road, while a concrete bridge was constructed over the AB&A cut (later used by the Atlantic Coast Line Railroad, now CSX.)
A historical marker at the location of the crossing was erected by the Birmingham-Jefferson Historical Society. It was added to the Alabama Register of Landmarks and Heritage on July 15, 2021.
- "The Cut That Created Birmingham: The South & North Alabama Railroad at Brock’s Gap (1871)" (March 2021) Birmingham Historical Society Newsletter
- Brock's Gap at bhamrails.info