Direct link to Gibson County's INGenWeb Project site, as well as a link to the Gibson County Cemeteries database through INGenWeb. The cemeteries database is organized by township: Barton, Center, Columbia, Johnson, Montgomery, Patoka, Union, Wabash, Washington, and White River. Another view of this database can be found here.
From their site: "Our goal is to provide free data online to help you find your family ancestry. We regret that we are unable to perform personal research for folks. All data we come across will be added to this site. We are constantly looking for new data to post."
There are four public libraries that serve Gibson County. I've listed them below, along with their building locations (in parentheses).
Fort Branch-Johnson Township Public Library (Fort Branch, IN & Haubstadt, IN)
Oakland City-Columbia Township Public Library (Oakland City, IN)
Owensville Carnegie Public Library (Owensville, IN)
Princeton Public Library (Princeton, IN)
From their site: "The Gibson County Civil War Memorial was erected in 1912 by the citizens of Gibson County in honor of the 2,200 soldiers and sailors who enlisted from Gibson County in the Civil War from 1861 to 1865. The monument is in Princeton, Indiana, at the intersection of Broadway and North Main streets."
History of Gibson County, Indiana by James T. Tartt & Co. (1884)
The Pictorial Story of America: Containing the Romantic Incidents of History, from the Discovery of America to the Present Time by Elia Wilkinson Peattie (1895)
An entire section on Gibson County, Indiana is in PART III (pages 1120-1272; this is out of the total 1284 pages of this digital file).
History of Gibson County, Indiana: Her People, Industries and Institutions by Gilbert R. Stormont (1914)