US President Donald Trump has ordered the release of nearly 3,000 files on John F Kennedy assassination.
But he blocked the release of other files, citing national security concerns.
Senior administration officials did not divulge the contents of the files being shared by the National Archives on Thursday.
Conspiracy theories have swirled since President Kennedy was fatally shot in Dallas, Texas, on 22 November 1963.
The CIA, FBI, Department of State and other agencies were reportedly engaging in last-minute lobbying of the White House to keep certain documents under wraps.
Some redacted documents are undergoing a further six-month review, but it is possible those records could stay secret even after the 180-day period.
One White House official told Reuters news agency: “The president wants to ensure there is full transparency here and is expecting that the agencies do a better job in reducing any conflicts within the redactions and get this information out as quickly as possible.”