I put this post in Don's thread, but it bears repeating here. My explorations were prompted by Tom and Joyce on C Otter, who are the organizers, and know the river very well.
The St. Johns River is my favorite river in N. America. There are many places to explore off the main river. Some parts are basically unchanged for several hundred years. There are evidences of the indigenous peoples who lived there for centuries.
There are some great books on the River.
The River of Lakes:
Exploring the St.Johns
Travels on the St. Johns
St. Johns River Guide book
St. Johns & Ocklawaha Rivers (Images of America: Florida)
There are 3 fishing maps--great for exploring
There are the NOAA charts -free print outs, or you can buy hte booklets.
For many years the Railroad stopped at Jacksonville and the wealthiest of America would then take steam ships up the river to verious spas and estates. Some of these are still standing. After Flagler built the railroads to Miami and the keys, the St. John's fell out of favor
Audubon explored the lower reaches, and studied some of the birds. I was disappointed to learn he killed each bird he studies.
Harriet Beecher Stowe lived on the St. Johns River. (Uncle Toms Cabin) and Marjorie Kinnan Rawlings's (The Yearling) Both lived along the St. John's River.
William Bartram wrote about the nature, Indians and trading posts on the St. Johns when he visited the River.
If you get a chance try and go up the Econlockhatchee River (Econ) to the. outskirts of Orlando. It is often impassible. I am aware of about 5 Dory owners who had done at least part of the Econ