Historical theology is Scriptural theology organized and viewed through the way it has been recognized and developed through the history of the Church.
Why is historical theology dearly precious? Because nearly every aspect of Scriptural teaching has been hammered out in more profound earnestness and depth by the godly giants of the past, and their personal stories, than we can comprehend.
Here is a collection of the major historical theologies on the net:
May you find it a blessing.
We now have rather full collections at ReformedBooksOnline of the three main divisions of theology: Historical, Biblical and Systematic.