I don't know which of the Census 2000 summary files I need. What are the differences?
The four summary files below for Census 2000 are among the most detailed data products available from the population and housing census.
All four files show data for states, the District of Columbia, Puerto Rico, counties, county subdivisions, cities, American Indian and Alaska Native areas, Hawaiian Home Lands, and census tracts. SF 1 has the most geographic detail, with data for census block groups and blocks; SF 3 has data for block groups. Both SF 1 and SF 3 have data for ZIP Code Tabulation Areas®, Congressional districts, and metropolitan areas.
SF 1 and SF 3 have data on a larger set of topics than do SF 2 and SF 4. What makes SF 2 and SF 4 special is the vast data on population subgroups found on these files.
SF 2 repeats tables for up to 249 race (e.g., Black, Chinese, Asian Indian, etc.) and Hispanic/Latino groups (e.g., Mexican, Cuban, Salvadoran, etc.), as well as American Indian and Alaska Native tribes. SF 4 repeats tables for these groups and also for up to 86 ancestry groups.
If you want to get started, the Census 2000 Gateway page is a good place to find links to Census 2000 data and reference information.