The son of a charter member of the plumbers union, Henning rose to become the longtime head of the California Labor Federation before his retirement in 1996.
As the state's top labor advocate for more than a quarter-century, Henning gained legendary status as a fierce defender of workers and an avid foe of the perils of "capital" left unchecked.
"His commitment to global unionism and anti-racism were ahead of his time, and he never hid from a good fight," said Art Pulaski, who succeeded Henning as head of the labor federation and still holds the post.
Luminaries including Gov. Arnold Schwarzenegger and U.S. Labor Secretary Hilda L. Solis paid posthumous tribute to Henning's lifelong commitment to workers' struggles.
"Jack Henning was a champion, visionary and unwavering voice on behalf of the working women and men of the United States and the world," Solis said. "We are all indebted to his leadership, and he will be missed."
Henning was a close ally of Cesar Chavez, the late leader of the farm workers, and cited among his proudest accomplishments passage in 1975 of the landmark Agricultural Labor Relations Act, which gave new protections to field hands.
"Jack never wavered, whether it was standing . . . on the picket lines in the dusty fields and vineyards or in the halls of the state Capitol," said Arturo S. Rodriguez, president of the United Farm Workers.
Henning faced an 18-year reign of Republican governors while he served as organized labor's chief advocate before state lawmakers. Supporters cite a rich legacy of improvements in working conditions, minimum-wage guidelines, labor standards, workers' compensation and child-labor laws, among other arenas.
Henning's oratorical skills were renowned, delighting spellbound union conventioneers, though he never took a note to the podium, Pulaski said.
He routinely thundered from the political left against the scourge of unbridled and unequal wealth, a white-haired lion spewing disdain on those unmoved by the plight of the underclass.
In his farewell address from the federation in 1996, Henning dared conservatives to go to any major U.S. city "and see what capital has done to the poor . . . see the homeless, beggars at the table of wealth. . . . Let the defenders of the established order live with that moral outrage. Their day will come."
Before taking the helm of the California Labor Federation, Henning had served as U.S. undersecretary of labor in the Kennedy and Johnson administrations. Johnson also appointed him ambassador to New Zealand, a post that Henning relished, given his working-class origins.
His father's 3-foot-long steamfitters pipe wrench, now copper-plated, adorned his office for decades.
Despite his widespread popularity, Henning was not immune to criticism, especially as union membership and clout diminished in the late 20th century.
Henning, like other traditional union leaders, tended to blame labor's diminished sway on the decline of traditional, heavily unionized smokestack industries. But others argued that organized labor in California and elsewhere was slow to adjust to the shifting economy and target high-technology jobs and other growing sectors, as well as reaching out to new-immigrant workers.
John F. Henning was born Nov. 22, 1915, in San Francisco. His plumber father was thrown out of work for almost a year during an anti-union drive after World War I, according to his official labor biography.
Henning joined his first union not long after graduating with a degree in English literature from St. Mary's College, and steadily rose in the ranks of the state and national movement.
He also served 12 years as a regent of the University of California, where he fought for affirmative action and led a successful fight to have the university divest in apartheid South Africa.
At his farewell speech from the federation in 1996, Henning elicited thunderous applause with his closing words: "And if by a suspension of the laws of nature I were young again, I would follow no other course, no other flag but the flag of labor."
Henning is survived by sons Brian of San Francisco, Daniel of San Rafael, John Jr. of Petaluma, Patrick of Sacramento and Thomas of Moraga; daughters Mary of San Francisco and Nancy Goulde of Amherst, Va.; 12 grandchildren; and six great-grandchildren. His wife, Betty, died in 1994.
Final details on services are pending.