Barry, it looks like the Lincoln Highway logo to me but I haven't researched the route, so I'm not certain.
Regards,
Art S.
In picture #4: Is that the blue "L" logo of the Lincoln Highway painted on it? Comparing the steel members with the size of the cars and people, I can see that this was a very heavily built bridge.
Nice write-up on the history of the bridge:
http://journalstar.com/news/state-and-regional/nebraska/jim-...
Yes, the Ak-Sar-Ben Bridge was part of the Lincoln Highway.