History of the unraveling of the natural decay series

Milestones in the subject of radioactivity, which were important to the unraveling of natural decay series, have been identified and described. The interplay between all these issues is very complex, and some aspects of the development of the uranium series is discussed as an example, the thorium and actinium series evolved in a similar way from research by many of the same people. All three series as understood in 1913 are compared with their present-day representation.