"Jack was the best friend Republic Pictures ever had," Magers said. "He elevated Republic to a place in history that I feel it earned."
Although Republic occasionally turned out high-profile films such as "The Quiet Man" and "Sands of Iwo Jima," Magers said, it was better known as the action studio and serial factory. "And the serials they turned out were 10 times better than what Columbia or Universal were turning out. Jack captured all that," he said.
Mathis went on to write and publish "Valley of the Cliffhangers Supplement" (1995) and the first two volumes of his planned trilogy: "Republic Confidential: The Players" (1992) and "Republic Confidential: The Studio" (1999).
"Jack made so many people aware of what Republic Pictures gave us," said Magers. "They had Roy Rogers, Gene Autry, Sunset Carson, the Three Mesquiteers, Don Barry, Wild Bill Elliott, Rex Allen -- all the biggest and the best of the B-western stars worked at Republic.
"The other thing about Jack is he did it all with love. This was not something he did to make money."
Mathis had relatively small printings for his books -- 5,000 copies in the case of "Valley of the Cliffhangers," which was sold out by 1981.
"I don't even know if he broke even when you consider all the trips to California," Mathis' wife, Dene, said. "It was a labor of love for him. He just loved those movies."
Despite her willingness to sit through repeated viewings of serials such as "Captain Marvel" and "King of the Royal Mounted" with her husband, she drew the line when he wanted to name their daughter Nyoka, after the title character in the Republic serial "Perils of Nyoka."
After "Valley of the Cliffhangers" was published, Mathis received letters of thanks from fans of the old serials -- and from many of the actors who worked in them, including Richard Webb, Clayton Moore, Duncan Reynaldo and Kirk Alyn.
"It's of no great consequence," Mathis told the Chicago Tribune in 1989, "but what a delight it is to pick up one's morning mail and find a personal letter from Captain Midnight, the Lone Ranger, the Cisco Kid or Superman."
Several years ago, Mathis donated his Republic files, films, videotapes and audiotape interviews to the library at Brigham Young University in Provo, Utah.
Mathis was at his desk working on the layout of his final book, Volume 3 in the "Republic Confidential" trilogy, "The Films," when he died.
"He was on Page 453 and almost finished," said his daughter, Jana.
Mathis, who had been helped in writing synopses of the Republic films by Sherman Oaks writer Woody Langley, had planned to publish next spring. His wife said she hopes to see the book completed.
"That's the one that everybody's been waiting for," said Magers.
In addition to his wife and daughter, Mathis is survived by a son, Kane; and a granddaughter.
