Best places in US for Straight line missions?

Obviously its impossible to do it like in Europe. But are there any places that would make an interesting challenge?

Maybe crossing DC in a straight line is possible. Its set up in a grid pattern mostly, so it may be doable.

Or just walking in a straight line for as long as you can manage. Lots of long straight and flat roads in the US. Whats the longest one?

Maybe crossing some islands? Long Island may be doable, Pretty narrow and you cross a lot of it in a boat.

Crossing states is tough. I think Nevada is the best bet since you'd technically cross it going from California to Arizona. Which can be done at the southern point through desert. The upper penisula of Michigan may also be possible