Gibson/Gipson Cook appears in the 1870 and 1880 Census Records of Warren County, Virginia.

You may want to order his Compiled Service Record:
http://history-sites.com/research/index.html

Seek out regimental histories:
http://www.worldcat.org/oclc/51088918&referer=brief_results
http://www.worldcat.org/oclc/7646081&referer=brief_results

Investigate sources in Warren County:
http://users.erols.com/va-udc/museum.html
http://www.rootsweb.ancestry.com/~vawarren/warren.htm