I think in Texas, it would be at this point on the Rio Grande east of Big Bend, which is 44 km (27 miles) from anyplace GoogleCar has ever been. There actually appears to be a road going down there.
https://maps.google.com/maps?ll=29.7...04656&t=h&z=18
It is apparently not possible to copy a Google map with the measurement tool markers in place. But you can locate your selection and post it, so other users can zoom out and see its location.
Activate the measurement tool by clicking the icon left of the measurement scale, lower left of the map. If you don't see the icon, click on the extremely tiny words "Maps labs" just above the copyright notice in the lower left of your Google Maps screen, and Enable Measurement Tool. Google, still the leader in intuitive user-friendly websites.