I came across the C++ Historical Source Archive through LtU. It is a treasure! Paul McJones, the editor maintaining it, mentions his effort with Bjarne Stroustrup, the author of C++.
The archive provides the various releases of Cfront, one of the early C++ compilers that converted C++ to C. It also provides links to standardization documents and other research papers. The only other similar documented effort is The Design and Evolution of C++ book. The team is also looking for pre-1990 applications developed using C++.
A great resource, not only for a C++ fan like me, but also for anyone wanting to track evolution of a programming language.
