The 342nd Engineer General Service Regiment was activated in April of 1942 at Camp Claiborne, Louisiana and sailed from New York to England in July 1942. Arrived In France at Omaha Beach 12 June 1944. On the 17th June they repaired the rail line north of Carentan then assisted in thr repair & reconstruction of the port of Cherbourg. Later the regiment played a major role in the completion of the Cherbourg to Paris Railroad. The regiment also served in the Ardennes ? Alcase and Rhineland campaigns.
There is a book of the unit history, but you may have to search used book sellers to find a copy or do a WorldCat search to find it in a library.
A History of the 342nd Engineer Regiment (General Service), United States Army Reserve, 1921-1948
United States. Army. 342d Engineers, Charles Harvey Roe, 1958