The Seymours’ work, which traced organized baseball from its roots until 1930 in the first two books, then detoured to a focus on amateur baseball in the third, has long been considered the first significant scholarly account of baseball’s past.

Her friend Charmaine Wellington said the cause was complications of an ulcer.

NEW YORK — Dorothy Seymour Mills, who collaborated for more than 30 years on a landmark three-volume history of baseball with her first husband, Harold Seymour — although he refused to credit her — died on Nov. 17 in Tucson. She was 91.

“No one may call himself a student of baseball history without having read these indispensable works,” John Thorn, Major League Baseball’s official historian, wrote in Baseball Research Journal in 2010.


Ms. Mills played numerous roles in the creation of “Baseball: The Early Years” (1960), “Baseball: The Golden Age” (1971), and “Baseball: The People’s Game” (1990). She was their primary researcher, scouring libraries and archives throughout the country; she organized the project, edited the books before they were submitted for publication, typed the manuscripts, and prepared the indexes; and she wrote a large part of the final book.

Yet each volume bore only Seymour’s name. When the first book was published, Sports Illustrated compared him to Edward Gibbon, author of “The History of the Decline and Fall of the Roman Empire.”

In each book, Ms. Mills was simply one of many people thanked in the acknowledgments. In “The “Golden Age,” Seymour cited her for having “contributed her knowledge and professional skills to all phases of the work.”

In 1989, as they were nearing completion of “The People’s Game,” Dorothy Mills formally pressed her husband for coauthor status. Seymour’s declining health meant that she had done more than usual. She had also written the last 13 of its 37 chapters.She presented him with a 12-point demand for recognition.


In her second point she wrote, in part: “I sifted, analyzed, and organized all the research, putting it into a form that would make it intelligible and from which the writing could be done. I produced hundreds of pages of outlines interpreting as well as quoting from the research.”

She added, “Without this analytical study, the writing would have been impossible.”

Seymour denied her.

It would take nearly 20 years after Seymour’s death in 1992 for Ms. Mills to get her due.

Dorothy Jane Zander was born on July 5, 1928, in Cleveland. Her father, Henry, was a printer. Her mother, Katherine (Reinert) Zander, was a homemaker.

By her high school years, Dorothy was smitten by the English language, its grammar and history, and by the authors Upton Sinclair and Thomas Mann. With an eye on a journalism career, she edited her high school newspaper and was a clerk for The Cleveland News.

At Fenn College (now Cleveland State University), she studied English and met Seymour, 18 years her senior, who was her professor for history courses. While she was still a student, Seymour hired her for secretarial work and began using her writing skills to help him prepare his courses. Soon, she started helping him with his doctoral dissertation on early baseball history.

He was a baseball fan — he had been a batboy for the Brooklyn Dodgers at Ebbets Field — and she was not.

“People can’t understand that,” she told the Times. “I think it’s a good idea to remain above that. You write a lot more objectively about a subject you’re not in love with.”


They became increasingly close and married after her third year at Fenn.

After Seymour died, she began to publicly discuss her role in his work, and to write about it. But nearly two more decades passed before her name was finally on the baseball books.

It began with another vexing reminder of her husband’s refusal to credit her. In 2010, the Society for American Baseball Research (SABR) announced that Seymour — not Ms. Mills — would be among those receiving the inaugural Henry Chadwick Award, which honors baseball researchers.

After objections from many of SABR’s female members, the selection committee reversed itself. Ms. Mills was added to the list of awardees.

Four months later, Oxford announced that future printings of the “Baseball” trilogy would bear Ms. Mills’s name.

By then, Ms. Mills’s life had changed significantly.

She had met and married Roy Mills, a former officer in the Royal Canadian Air Force, in the 1990s. And she wrote historical novels.

She was also the author of “Meatless Meat” (2001), a book of vegetarian recipes; a series of mysteries set inside an assisted living facility like one where she lived; and “Chasing Baseball: Our Obsession With Its History, Numbers, People, and Places” (2010).

Ms. Mills, who lived in Tucson, leaves her stepdaughter, Mary Jane Webb; her stepsons, David, Kenneth, and Donald Mills; and six grandchildren. Roy Mills died in 2012.