Halfway Points on the trail

How many "half way" points can you have? It turns out that there are three...

1. The "traditional" halfway point. Many years the trail is re-routed somewhere and the exact mid-point moves. A sign has been at the traditional midpoint for several years now.

2. The mathematically correct mid-point. A new sign is being erected. Here is a picture of me next to the temporary sign.

3. The psychological mid-point which is Harpers Ferry, West Virginia. The ATC (Appalachian Trail Conservancy) office is located there and they take your picture and note your name in a book. It is about 40 miles south of the exact point, but they can't just move the ATC office every year, can they?