There was and may still be a monument to General Forrest on Mud Island, not far from the location of the Forrest family home in Memphis, near the pavillion where the WWII bomber Memphis Belle sat on display for years.
The plane is now undergoing a fuill restoration at Wright Paterson AFB in Ohio, but so far as I know the memorial remains.
General Forrest is interred at Arlington National Cemetary, formerly home of the Robert E. Lee family's estate.
FORREST, NATHAN B
BRIG GEN 402 COMBAT WING AAF USA
VETERAN SERVICE DATES: Unknown
DATE OF BIRTH: 04/07/1905
DATE OF DEATH: 06/13/1943
DATE OF INTERMENT: 11/15/1949
BURIED AT: SECTION 11 SITE 824-A
ARLINGTON NATIONAL CEMETERY
