where is it?

[pdlethbridge]

Somewhere in the United States, you can go over 70 miles without making a turn. where is it?

[Santa Fe buff]

US 50, Nevada?

[thirdrail]

It's in North Carolina on the "A-line" of CSXT, formerly the main line of the Atlantic Coast Line. Rode it in 1991 on a CSXT OCS. 

[pdlethbridge]

another winner!
" Between Laurel Hill and Acme, CSX's line doesn't stray off course for 78 miles. Stand at grade crossing along the route and the headlight of the oncoming train is visible for several minutes before it comes near. Watch from the small town of Maxton."

[pdlethbridge]

When I saw this I said, Na, its got to be out west some where

[ebtnut]

FWIW, the longest piece of straight track in the world is in Australia--something over 300 miles!

[pdlethbridge]

If you look at it from the side, its shaped like a boomerang!

[glennk28]

Besides on the old Seaboard Air Line (where they got the name) there was the D&RGW"s line up the San Luis Valley in Colorado, a stretch between Alamosa and Salida.  You can still see the grade.