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Although it is not electronic you could try "Population History of
Eastern U.S. Cities and Towns, 1790-1870" by Riley Moffat, Scarecrow
Press, 1992. Also "Population History of Western U.S. Cities and
Towns, 1850-1990" by Riley Moffat, Scarecrow Press, 1996.  For places
in the eastern U.S. since 1870 John Andriot's "Population Abstract of
the United States" has figures for places over 10,000. There are
other sources that give comparative data depending on the census
and/or the state as well.
 
Riley Moffat
Brigham Young University-Hawaii