Northwest corner of Texas
In this photo, I am standing (as close as I could figure) on the northwest corner of Texas' panhandle. There was a USGS benchmark in the grass on the shoulder behind me that indicated the actual point was a certain number of feet in this direction. So the corner is right in the middle of US Highway 56/64/412. The north state line is the dirt road behind me (on which my car is parked).
If you haven't ever looked closely at a decent map of this area, you might be inclined to believe that my camera is in New Mexico, and that everything behind me and north (left) of the dirt road would be part of Oklahoma's panhandle. Actually, that's all part of New Mexico. New Mexico "wraps" around the Texas panhandle for a mile or two before it reaches Oklahoma. The southwest corner of Oklahoma's panhandle is a mile or two east (behind me) on the dirt road.