Conversation so far:
When did William Bartram return to Philadelphia?
Bartram returned to Philadelphia in January 1777.
Where did William Bartram return to Philadelphia from?
William Bartram returned to Philadelphia after exploring Cherokee nation.
What did William Bartram do on his return to Philadelphia?
William Bartram assisted his brother John in all aspects of running Bartram's Garden.
What types of things did William Bartram do for Bartram's Garden?
What else did William Bartram do in Philadelphia besides running the Bartram's Garden?
In the late 1780s, he completed the book for which he became most famous, Travels through North and South Carolina, Georgia, East and West Florida, the Cherokee Country, etc..

Question: What book?
Self-contained rewrite: What book did William Bartram complete in Philadelphia?