Yep, very interesting times back in the day. I have a very large collection - not just Nebraska and not just football - but it includes stamps, transfers, deeds, etc. and they were doing whatever they could to increase their population base. The dust bowl and blizzards crushed a lot of states - Nebraska was in the middle of it.
Los Angeles and southern California didn't necessarily care that Nebraska was using the phrase America's White Spot because LA used it in the 20s. However, there were more racial overtones associated with LA's use of the slogan.
