Lena Reinhardt mentions several historical milestones in developer productivity, including the publication of the first book on Extreme Programming (XP) in 1999, the Agile Manifesto in 2001, the Software Craftsmanship Manifesto in 2009, the founding of the DevOps Research and Assessment (DORA) in 2015, and the publication of the book 'Accelerate' in 2018. The SPACE framework, which expanded on these concepts, was published in 2021.