Great overview information, dates, details, related innovations, contributing factors and names of significant contributors to various inventions and/or categories of innovation (steam, electricity, transportation).
An Encyclopedia of the History of Technology [ONLINE] by 
Biographical Dictionary of the History of Technology [ONLINE] by A multidisciplinary online collection of subject-specific encyclopedias, subject-specific dictionaries and companions.
Good for looking up the name of a historically significant person, a historic event or a theory or phenomenon.
