It was listed on the U.S. National Register of Historic Places in 1991 .
The Ilik River Fortification II near Yona , Guam was built by Japanese forces during World War II .
Guam was listed on the U.S. National Register of Historic Places in 1991 .
The Ilik River Fortification II near Yona , Guam was built by Japanese forces during World War II .