In the decades after that, he wrote largely polemical articles and columns, in print for publications like Foreign Policy Journal and Counterpunch and later online. He also produced, and contributed to, exposés in books and other media about what he called misdeeds by the United States at home and abroad that were carried out in the name of national security.

Faking a flat tire near the gate to Central Intelligence Agency headquarters in Virginia, he surreptitiously recorded the license plates of employees who were entering and leaving. He revealed the names and home addresses of more than 200 of them in his book “The CIA, a Forgotten History: U.S. Global Interventions Since World War 2” (1986).

“They could have been spies,” said Louis Wolf, a founder with Mr. Blum in 1978 of what is now called CovertAction Magazine. “They could have been clerks.”

In an interview with The Washington Post in 2006, Mr. Blum encapsulated his life’s mission as “ending, at least slowing down, the American Empire,” or “at least injuring the beast.”

Still, no one was more surprised than he when a recording emerged in 2006 on which Osama bin Laden recommended that all Americans read Mr. Blum’s book “Rogue State: A Guide to the World’s Only Superpower,” first published in 2000 and updated in 2005. It vaulted almost overnight from about 205,000 on Amazon’s sales ranking to the top 50. (It stood at about 58,000 a few days after Mr. Blum’s death.)