An array of US local authorities – police chiefs, prosecutors, pastors and scout leaders among them – quietly shielded scoutmasters and others who allegedly molested children, according to a newly opened cache of confidential files compiled between 1959 and 1985.

At the time, they justified their actions as necessary to protect the reputation and good works of the Boy Scouts of America. But, as detailed in 14,500 pages of secret "perversion files" released on Thursday by order of the Oregon supreme court, their manoeuvres protected suspected sexual predators while victims suffered in silence.

The files document sex abuse allegations across the country, from a small town in the Adirondacks in New York state to downtown Los Angeles.

At a news conference on Thursday, Portland lawyer Kelly Clark attacked the scouts organisation for its continuing attempts to keep the files secret.

"You do not keep secrets hidden about dangers to children," said Clark, who in 2010 won a landmark lawsuit against the Boy Scouts on behalf of a plaintiff who was molested by an assistant scoutmaster in the 1980s.

The files were shown to a jury in a 2010 Oregon civil suit that the scouts lost, and the Oregon supreme court ruled the files should be made public. After months of objections and redactions, they were released.

The new files are a window on a much larger collection of documents the Boy Scouts of America began collecting soon after its founding in 1910. The files, kept at its headquarters in Texas, consist of memos from local and national executives, handwritten letters from victims and their parents, and newspaper clippings about legal cases. They contain details about proven molesters, but also unsubstantiated allegations.

Many of the files released on Thursday have been written about before, but this is the first time the earliest ones have been put in the public domain.

The 1959-85 files show that on many occasions the files succeeded in keeping paedophiles out of leadership positions – the reason they were collected in the first place.

But in many instances – more than a third, according to the organisation's own count – police weren't told about the alleged abuse.

And there is little mention in the files of concern for the welfare of scouts who were allegedly abused by their leaders. But there are numerous documents showing compassion for suspected abusers, who were often sent to psychiatrists or pastors to get help.

One of the most startling revelations is the frequency with which attempts to protect scouts from alleged molesters collapsed at the local level, at times in collusion with community leaders.

On the afternoon of 10 August 1965, a distraught Louisiana mother walked into the sheriff's office. A 31-year-old scoutmaster had raped one of her sons and molested two others, she said.

Six days later, the scoutmaster sat down in the same station and confessed.

But the decision was made not to pursue charges. "This subject and scouts [leaders] were not prosecuted," a Louisiana scouts executive wrote to national headquarters, "to save the name of Scouting."

In a statement on Thursday, Boy Scouts spokesman Deron Smith said: "There is nothing more important than the safety of our scouts."

Smith said there had been times when the organisation's responses to sex abuse allegations were "plainly insufficient, inappropriate, or wrong" and it extended its "deepest and sincere apologies to victims and their families".

The Boy Scouts recently made public an internal review of the files and said it would look into past cases to see whether there were times when abusers should have been reported to police.