BLK String 15 Census Block (SSCCCTTTTTTBBBB) POP100 Integer 9 Population of Census Block HU100 Integer 9 Housing Units in Census Block KEY090 String 23 SF3 Summary level 90 Block Group containing block LOGRECNO String 7 SF3 Logical record number for Block Group SL90POP100 Integer 9 Population of Block Group SL90HU100 Integer 9 Housing Units in Block Group Summary level 90 is the lowest level of data available in SF3. It is defined as: State (SS) County (CCC) County Subdivision (DDDDD) Place/Remainder (PPPPP) Census Tract (TTTTTT) Urban/Rural (U) Block Group (G) Key90 is of the form SSCCCDDDDDPPPPPTTTTTTUG. This file provides a correspondence between Census Blocks and summary level 90 Block Groups utilizing geographic information for blocks in TIGER 2002 as well as the population and housing units for both the Block and the containing Block Group, and the logical record number for SF3 data for the Block Group.