Brock Gap (variant Brock's Gap) is a natural pass across Shades Mountain in Hoover, Alabama, most notable as being the location used by the South & North Railroad (S&N) to reach the Birmingham area in the late 19th century from the mineral deposits to the south, spurring economic development in the area.

[1][2] John Milner was tasked by the State of Alabama in 1858 to survey a route across Shades Mountain for the S&N Railroad.

Brock Gap was selected and the rail line north was constructed between 1858 and 1871, interrupted by the Civil War.

At Brock Gap, workers used nitroglycerin to blast a cut 75 feet deep through limestone bedrock.

The direct successor of the S&N Railroad, the CSX S&NA South Subdivision, is carried through a more recently constructed tunnel slightly east of the 19th century cut.