The book series' origins came from Harold Seymour's 1956 Ph.D. dissertation which was entitled The Rise of Major League Baseball to 1891.

Dorothy wrote most of the third volume herself as Harold's health had deteriorated significantly and he was suffering from Alzheimer's disease.

[2] In 2011, Oxford University Press co-credited Seymour Mills as the co-author of the trilogy, alongside her husband, finally acknowledging her contributions to baseball, with her name coming first on the third book which she almost entirely written herself.

The book notably successfully debunked the myth that Civil War General Abner Doubleday invented baseball.

It also covers the onset of the live ball era, after the notorious Black Sox scandal threatened to tarnish the game, and how the business model evolved as a result.