The Census Bureau (http://www.census.gov/) maintains geographic boundaries for the analysis and mapping of demographic information across the United States. Every 10 years the Census Bureau counts the population of the United States as mandated by Constitution. The Census Bureau releases the results of this county as demographic data with geographic identifiers so that maps and analysis can be performed on the US population.

What is unique about LA County’s data?

It is clipped to the ocean boundary. Raw Census data includes a 3 mile buffer into the ocean, which impacts cartography.

IMPORTANT! It has been updated to the 2012 Census Geography Update, which merged Tracts 1370.00 and 9304.01 into the combined tract 1370.00. So the CT10 field actually reflects the 2012 Census update, which is used for all population products 2012 and later. CENSUS_TRACTS_2010 will reflect such change and CENSUS_TRACTS_2010_ORIGINAL will not reflect such change.

How was this data created?

This data was downloaded from Census Bureau website: http://www.census.gov/cgi-bin/geo/shapefiles2010/file-download and clipped to the County Boundary using ESRI’s ArcGIS Desktop. Two new fields were added in census tract data – area in square feet and shape length in feet. This dataset has unique identifier field “GEOID10” for each record and the census tract number fields “CT10” and “LABEL” (6-digit number and 6-digit number with decimal point, respectively).

2010 Census Blocks clipped to the County Boundary. A new field “COMMNAME” was added and populated with city and community names based on 2011 redistricting unit community names in the census block data.

2010 Census Tracts clipped to the County Boundary. Two new fields were added to this census tract data – area in square feet and area in square miles.