David --

Someone who knows Mobile County may be able to offer a better site location. Older maps place Halls Mill on the north side of Dog River, middle fork, about where Government Blvd crosses the stream.

An 1889 map displays small circles with a flag icon inside the circle to mark camps, fortifications and other Civil War sites. The map has a flag icon where the old Government Road bridge crossed the creek. Note: this road is west of Hall's Mill Road.

To access the Mobile County map page, copy and paste this link:
http://alabamamaps.ua.edu/historicalmaps/counties/mobile/mobile.html

Look for the Paul C Boudousquie map, published in New Orleans, 1889.

Hall's Mill location on the 1890 map just below the Boudousquie map:
Range 2W, Twp 4S, covering south half of Section 15 and north half of Section 22.
Would expect to find camps on high ground, north and south of the stream. The part north of the stream is probably along the eastern side of the Vista Ridge Park. neighborhood.