Backpack system with interchangeable elements

A backpack apparatus comprising:

• a backpack harness comprising a vertical support element, shoulder straps and a hip belt, the shoulder straps, and hip belt coupled to the vertical support element, the backpack harness comprising a first portion of a coupling mechanism and a first portion of a coupling;
• an external frame comprising a second portion of the coupling mechanism and a first portion of the coupling and a second portion of the coupling, wherein the external frame releasably couples to the backpack harness by coupling the first portion of the coupling mechanism on the backpack harness to the second portion of the coupling mechanism on the external frame and the first portion of the coupling on the backpack harness to the second portion of the buckle coupling on the external frame;
• and
• a backpack comprising a second portion of the coupling mechanism and a second portion of the coupling, wherein the backpack releasably couples to the backpack harness by coupling the first portion of the coupling mechanism on the backpack harness to the second portion of the coupling mechanism on the backpack and the first portion of the coupling on the backpack harness to the second portion of the coupling on the backpack, and the backpack releasably couples to the external frame by coupling the first portion of the coupling of the external frame to the second portion of the coupling of the backpack,
• wherein, when the backpack apparatus is worn by a user, each portion of the coupling mechanism is located on a lower portion of the backpack harness, the external frame and the backpack and each portion of the coupling is located on an upper portion of the backpack harness, the external frame, and the backpack, wherein the lower portions are oriented toward the hips of a user and the upper portions are oriented toward the head of a user.