The "Manhattan project" was the code name for the project to develop the first atomic bomb.
A statement from the White House said that Jeffries's contributions to the U.S. military during World War II following his initial indictment on unlawful anticompetitive conduct merited a pardon for Jeffries, who was fined but never imprisoned for the conviction.
"One of America’s leading scientists, Dr. Jeffries was crucial to the United States war effort in World War II. His efforts enabled the United States to develop artillery shells capable of piercing the armor of German tanks, and his contributions to the Manhattan Project helped end the war in the Pacific theater," the White House said.
"Although indicted in 1941, Dr. Jeffries proved vital to the war effort prompting Secretary of War Stimson to take the extraordinary step of requesting, with President Roosevelt’s approval, that the Attorney General defer any prosecution until after the war," the statement continued.
Trump's interest in the case was spurred by Sen. Lindsey Graham (R-S.C.). Former Rep. Trey Gowdy (R-S.C.), now working with the White House in its defense against Democrats' impeachment efforts, also was involved in getting Jeffries's case before the president, according to the statement.