During a time of tumultuous relationships between the White House and the press, the era of the 1960s to the 1970s were fraught with discussions about what information the public had to a right to know versus what information the federal government had a right to keep to themselves.
Various senators and other governmental officials from both Democratic and Republican parties had taken stances on the issue for years. The FOIA was stalled through administration for the entire year of 1965, with federal agencies providing testimony and information which they felt justified the bill being vetoed.
However, by 1966, more specific wording was put into the bill explaining what types of information would be open to the public versus kept private. The bill passed unanimously.