Information about my grandfather

I found a few sources about the 116th AAA, but the first thing I'd do is make sure you have the right information by looking at his military records, they should tell you what units he was assigned to, what dates, and what awards he received. If you don't have his records, the National Personnel Records Center is the Federal repository of millions of military personnel, health, and medical records of discharged and deceased veterans of all services during the 20th century. (Records prior to WWI are in Washington, DC.) Information from the records is made available upon written request to the next of kin to the extent allowed by law.
http://www.archives.gov/st-louis/military-personnel/ and/or http://www.archives.gov/veterans/evetrecs/index.html

According to http://www.skylighters.org/aaapatches/index.html - The 116th served in the European Theatre of Operations, entering combat on June 7, 1944 (D+1) at Utah Beach, Normandy under the command of Col. James Shearouse. Batteries were attached to the 2nd, 5th (D Battery), 30th, and 35th Infantry Divisions for much of the campaigns in Northwest Europe. The 116th's 90-mm guns were also attached to the 654th Tank Destroyer Battalion during early August, deployed in an anti-tank role supporting the 654th in attacks against German armor operating in the vicinity of Vic Conde-Sur-Vire, France. They participated in the Battle of the Bulge and in the defense of the Ludendorff Bridge at Remagen, Germany in March 1945.

According to http://www.6juin1944.com/assaut/utah/page.php?page=fo1_11 - They have a copy of the orders assigning the 116th to D-Day.

According to http://www.military-network.com/Ben/Associations_Detail.cfm?ID=1196 - There is a 116th AAA Gun Bn Association. Contact person is Mr. William F Greischel (NJ) 973-697-7875

From a 2000 copy of the VFW Magazine - Reunion for the 116th AAA Gun Bn, all btrys & HQ: William F. Greischel (973) 697-7875

Article in the helenair.com from 2005 about the 116th AAA - http://www.helenair.com/articles/2005/03/07/helena/a08030605_01.txt

According to http://www.airdefenseartillery.com/online/HistFeatures/482nd.pdf - the 116th was attached to the 1st Army from 6 JUNE 1944-8 MAY 1945

According to the Army website at http://www.army.mil/d-day/forces.html - It lists the 116th AAA as one of the Army units that were awarded assault landing credit for the Normandy invasion, 6 and 7 June 1944.

Since you're in NJ, you can visit the Mudd Library, at Princeton, where there is a “The Skysweeper: A History of the 116 A.A.A. Group,” 1942 -1945 written by Robert Chaplin ’16, who served as the first group commander for the 116th Antiaircraft Artillery Group.
http://www.princeton.edu/pr/pwb/05/0911/5a.shtml and http://diglib.princeton.edu/ead/eadGetDoc.xq?id=/ead/mudd/univarchives/A...

Well that's about all I could turn up, but that should get you started.

Good Luck,