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Split 2010 Block Group/City – Community Statistical Area (formerly BASA)

basaThis dataset contains 2010 Block Groups, updated to improve geographic accuracy, split by City boundaries for each year since 2010.  It is a foundation-level dataset that is used to create many other datasets and reporting within the County, including:

Download the data

EGIS_BG10FIPxx_CSA_20170118 (zipped shapefile)


This data was created by combining the 2010 Census Block Group file as well as the Legal City Boundaries maintained by the LA County Department of Public Works.

In reviewing this overlap, LA County aligned a fairly large number of block group boundaries to city boundaries where those boundaries were identified as being incorrectly mis-aligned by the Census Bureau.  This removed split block groups that did not have any population assigned to them.

To support the BASA project*, some split block groups that had multiple parts were “unmerged” so that non-contiguous portions of the split block group could be assigned to different BASAs.  Examples include areas of Unincorporated Quartz Hill and Lancaster that have 2 or more BASA names for a single split block group.  Those portions are identified as “Parts” and tracked in the “Parts” field.

In the City of Los Angeles, the LA City Neighborhood file was overlaid on the Block Groups and boundaries assigned using the centroid of the block group – therefore, while the names of the BASAs in LA City match the neighborhood file, the boundaries are not the same.


*NOTE:  BASA renamed to Countywide Statistical Areas in July 2016.
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Data Field Descriptions

BG10 2010 Block Group (7 digits)
CT10 2010 Census Tract (6 digits)
FIP10 2010 City (5 digit FIPS code)
FIP11 2011 City (5 digit FIPS code)
FIP12 2012 City (5 digit FIPS code)
FIP13 2013 City (5 digit FIPS code)
FIP14 2014 City (5 digit FIPS code)
FIP15 2015 City (5 digit FIPS code)
FIP16 2016 City (5 digit FIPS code)
CITY_TYPE "City" or "Unincorporated"
LCITY Legal City Name
BASA Board Approved Statistical Area Name (e.g. Community)
LABEL Pretty name for Labelling
BG10FIP10 2010 Split Block Group
BG10FIP11 2011 Split Block Group
BG10FIP12 2012 Split Block Group
BG10FIP13 2013 Split Block Group
BG10FIP14 2014 Split Block Group
BG10FIP15 2015 Split Block Group
BG10FIP16 2016 Split Block Group
CT10FIP10 2010 Split Tract
CT10FIP11 2011 Split Tract
CT10FIP12 2012 Split Tract
CT10FIP13 2013 Split Tract
CT10FIP14 2014 Split Tract
CT10FIP15 2015 Split Tract
CT10FIP16 2016 Split Tract
DISTRICT 2011 Supervisorial District
NOTES Notes relevant to the geography
PART Part number (for non-contiguous split block groups)
PARTS Total number of non-contiguous parts (for non-contiguous split block groups)
BASA_ID Unique BASA ID - combination of 2016 Split Block Group and Part Number
MERGED Flag if the Split BLock Group was merged into multi-part shapes

GIS Source Information
Database Name: eGIS_Demographic
Feature Class Name: EGIS_BG10FIPxx_BASA
Feature Dataset Name (if applicable):
Reference Date: 2017
Accuracy: Parcel
Update Frequency: As Needed
Access Constraints:None

Contact Information
Steve Steinberg
Geographic Information Officer
Los Angeles County
Internal Services Department
9150 E. Imperial Hwy, MS#3
33.916650, -118.132255
Downey, CA 90242
(562) 392-7126

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