Suggested citation for tables found in print (pdf) census volumes*
U.S. Census of Population, 1960: Number of Inhabitants. Volume I Part A: Characteristics of the Population. Table 8: Population of all Incorporated Places and Unincorporated Places of 1,000 or more. Washington: Government Printing Office. [PDF document] http://www.census.gov/prod/www/decennial.html. Accessed 03/08/2016.
*I have not found citation rules that match this scenario in all of its particulars. This is more or less a "best practice" recommendation to include enough information to lead your reader to the specific table you consulted. Since I found this via the digitized pdfs hosted by the census bureau, I included the url and the date accessed.