[mpyne]

Another notable result of the 1980 census was that it was the first one where the majority of Americans lived west of the Mississippi River.

[hollerith]

Not true[1]. Perhaps the "population center of mass" is west of the Mississippi, but that is a different statistic.

[1] http://wiki.answers.com/Q/What_it_the_population_west_of_the...

[raldi]

As an example of how this could be possible, imagine the population of the USA were 3: two people living in East St. Louis, and one person living in Hawaii.

[inportb]

It would be fun to actually compute the center of mass, knowing that people are not uniformly massive.

[ekimekim]

A good starting point might be average weight statistics on a per-state level. I doubt you could get any finer-grained information though.

[mattst88]

Distance, as well as population, is a factor in the mean center of population. Even today there isn't close to a majority of the population living west of the Mississippi.

[mpyne]

Good point, I only wish I'd seen it in time to fix my comment.