These two quotes from Ms Armes are inaccurate. Robert C. Black II, The Railroads of the Confederacy, shows the Alabama and Tennessee Rivers R.R. as five-foot gauge built before the war, with no spurs or intersecting lines built during 1861-65. John T. Milner began cutting the bed for a line to Brock's Gap in 1858, but laid no track until 1869. The South and North R.R. line from Montgomery to Decatur remained incomplete until 1871.

Allow me to direct your attention to a historic marker 1,800 miles closer to you than me.
http://www.hmdb.org/marker.asp?marker=26773

Stewart's guide to historic railroads of Birmingham is a better resource. You will appreciate the 1858 place name refeences in Milner's 150 page report.
http://www.bhamrails.info/Milner_report_Gov.htm

You have better access to other sources on Frank Gilmer and John T. Milner and their work on the S&N line. Bottom line assertion -- work on the Brock's Gap line was underway during the war but incomplete until 1871.

The other source cited includes many other historic railroad markers from Alabama and indeed, the rest of the western hemisphere.