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2020 Census Block Relationship Files Record Layouts

Block relationship files are state-based tabular files comparing the universe of 2010 Census blocks to the universe of 2020 Census blocks.

These block relationship files identify states, counties, tracts, and blocks by their FIPS (Federal Information Processing Series) or census supplied geographic codes. These files do not include the geographic names referenced by the FIPS codes. Block relationship files are provided in a pipe-delimited Unicode Transformation Format 8-bit block (UTF-8) encoded text file format. The record layout is provided below.

Block relationships may be one-to-one, many-to-one, one-to-many, or many-to-many.  The Block Part Flag indicates whether the record for an individual block within any pairing of blocks represents all or a portion of the block.  For instance, in a one-to-one relationship between a 2010 tabulation block and a 2020 tabulation block, the block part flag for each will be blank, indicating that the 2010 tabulation block in its entirety is coextensive with the 2020 tabulation block.  In a many-to-one relationship, multiple 2010 tabulation blocks may be contained within one 2020 tabulation block.  In this instance, the block part flag for each 2010 tabulation block would be blank; the block part flag for the 2020 tabulation block record in each pair would be “P” since the 2010 tabulation block relates to only a portion of the 2020 tabulation block.

2010 Census Tabulation Block to 2020 Census Tabulation Block Relationship File Layout

Field # Maximum Length Field Name Field Description
1 2 STATE_2010 2010 tabulation state FIPS code
2 3 COUNTY_2010 2010 tabulation county FIPS code
3 6 TRACT_2010 2010 census tract number
4 4 BLK_2010 2010 tabulation block number
5 1 BLKSF_2010 2010 tabulation block suffix
6 14 AREALAND_2010 2010 Land Area
7 14 AREAWATER_2010 2010 Water Area
8 1 BLOCK_PART_FLAG_O 2010 tabulation block part flag; Blank = whole; P = part
9 2 STATE_2020 2020 tabulation state FIPS code
10 3 COUNTY_2020 2020 tabulation county FIPS code
11 6 TRACT_2020 2020 census tract number
12 4 BLK_2020 2020 tabulation block number
13 1 BLKSF_2020 2020 tabulation block suffix
14 14 AREALAND_2020 2020 Land Area
15 14 AREAWATER_2020 2020 Water Area
16 1 BLOCK_PART_FLAG_R 2020 tabulation block part flag; Blank = whole; P = part
17 14 AREALAND_INT Intersection Land Area shared by the 2010 and 2020 blocks represented by the record
18 14 AREAWATER_INT Intersection Water Area shared by the 2010 and 2020 blocks represented by the record




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