The hill is located 3 kilometres (1.9 mi) northeast of the confluence of the Yen, Ai Nghia, and La Tho Rivers and was a United States Marine Corps base during the Vietnam War.

[3] In early 1966, Hill 55 was the dominant terrain feature in the area of responsibility of the 9th Marine Regiment.

In March 1970, the 1st Marines transferred responsibility for the security of Hill 55 to the Army of the Republic of Vietnam (ARVN) 51st Regiment.

[8]: 37, 180  Combat operations by Marine, U.S. Army, ARVN, and South Korean soldiers against Communist forces in the area continued into 1971.

[8]: 118–35 This article incorporates public domain material from websites or documents of the United States Marine Corps.