WsMorrison,
I haven't played Rock Creek Park, but I have played the 18 hole and 9 hole courses at East Potomac Park, where Flynn evidently had some involvement.
My understanding of the architectural lineage of the 18 hole "Blue" course is that it was designed for the Park Service by Robert White around 1920, and having played a number of White's courses, it seems to fit the pedigree.
If Flynn was involved there, it was probably during the depression, and may have been a limited engagement.
The 9 hole "White" course is actually more interesting architecturally, although it is only 2,500 yards. While doing research a few years back, I came across information that indicated the White course was part of the original "West Potomac Park" course designed by Walter Travis and Dr. Walter Harban in the 20s, as well. For some time, the "West" course was primarily the "African American" course.
The green complexes of that course are significantly more interesting, and led me to believe that the Travis heritage is probably accurate.
I would certainly be very interested to hear from anyone who has further information. Craig Disher; you have a mission should you choose to accept it.
Mr. Morrison....I live in the Philly area, and I've done a lot of research on courses in the mid-atlantic region re: architectural heritage. If I can be of any help to your research, please just let me know. In any case, I'm excited to hear of your book about William Flynn, and wish you the best of luck.