Timelines under continual development by design.
Helpful maps for those who study the development of mathematics and science.
Chronologies Developed Here:
Statistical Mechanics
and Thermodynamics		 Hypercomplex Numbers Electromagnetic Theory
Chronologies From Elsewhere:
Wikipedia Timelines Timelines from the ever-expanding Wikipedia
HistoryOfScience.com History of Science, Medicine, and Technology
Timeline Index Many timeline cross-sections of history. Lots of interesting timelines from way way back to the present.
Maps of War History maps and timelines of religion, conquest, governments, etc.
A Timeline of Symmetry in Physics, Chemistry, and Mathematics A very well-researched timeline that I very much recommend. Also contains links to biographies as I have done in my timelines. Great to see such resources.
Chronology of Magnetospheric Exploration List of major events from 1600 to present, mostly in the 20th century, of course.